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317 lines
7.4 KiB
JavaScript
317 lines
7.4 KiB
JavaScript
1 year ago
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console.log("Hello B322!");
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// [SECTION] if, else if and else Statement
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let numG = -1;
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// if statement
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// executes a statement if a specified condition is true
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if(numG < 0) {
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console.log('Hello');
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}
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/*
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Syntax
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if(condition){
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statement
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}
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*/
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// The result of the expression added in the if's condition must result to true, else, the statement inside if() will not run.
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// You can also check the condition. The expression results to a boolean true because of the use of the less than operator.
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console.log(numG < 0);
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// results to true and so, the if statement was run.
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numG = 0
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if(numG < 0){
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console.log('Hello again if numA is 0!')
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};
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// It will not run because the expression now results to false:
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console.log(numG < 0);
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// Another sample
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let city = "New York"
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if(city === "New York"){
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console.log("Welcome to New York City!");
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}
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// else if Clause
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/*
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-Executes a statement if previous conditions are false and if the specified condition is true
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- The "else if" clause is optional and can be added to capture additional conditions to change the flow of a program.
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*/
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let numH = 1;
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if(numG < 0) {
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console.log('Hello');
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} else if (numH > 0) {
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console.log('Hello from the other side');
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}
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// We were able to run the else if() statement after we evaluated that the if condition was failed.
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// If the if() condition was passed and run, we will no longer evaluate to else if() and end the process there.
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let numA = -1
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if(numA > 0) {
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console.log('Hello');
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} else if (numH > 0) {
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console.log('World');
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}
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//else if() statement was no longer run because the if statement was able to run, the evaluation of the whole statement stops there.
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// Let's update the city variable and look at another example:
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city = "Tokyo"
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if(city === "New York"){
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console.log("Welcome to New York City!")
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} else if(city === "Tokyo"){
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console.log("Welcome to Tokyo, Japan!")
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};
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// Since we failed the condition for the first if(), we went to the else if() and checked and instead passed that condition.
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// let num = 10;
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// if (num > 0) {
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// if (num < 5){
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// console.log("Number is between 0 and 5");
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// }else {
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// console.log("Number is greater than or equal to 5");
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// }
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// }else {
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// console.log("Number is less than or equal to 0");
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// }
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// if (num > 0 && num < 5) {
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// console.log("Number is between 0 and 5");
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// }else if (num >= 5) {
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// console.log("Number is greater than or equal to 5");
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// }else{
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// console.log("Number is less than or equal to 0");
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// }
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if(numA > 0) {
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console.log('Hello');
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} else if (numH === 0) {
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console.log('World');
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} else {
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console.log('Again');
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}
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/*
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Since both the preceding if and else if conditions failed, the else statement was run instead.
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Else statements should only be added if there is a preceding if condition.
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*/
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// else {
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// console.log("Will not run without an if");
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// }
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// else if (numH === 0) {
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// console.log('World');
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// } else {
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// console.log('Again');
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// }
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// if, else if and else statements with functions
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/*
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- Most of the times we would like to use if, else if, and else statements with functions to control the flow of our application
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- By including them inside functions, we can decide when certain conditions will be checked instead of executing statements when the JavaScript loads.
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- The "return" statement can be utilized with condtional statements in combination with functions to change values to be used for other features of our application.
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*/
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let message = 'No message.';
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console.log(message);
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function determineTyphoonIntensity(windSpeed) {
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if (windSpeed < 30) {
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return 'Not a typhoon yet.';
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}
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else if (windSpeed <= 61) {
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return 'Tropical depression detected.';
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}
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else if (windSpeed >= 62 && windSpeed <= 88) {
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return 'Tropical storm detected.';
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}
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else if (windSpeed >= 89 || windSpeed <= 117) {
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return 'Severe tropical storm detected.';
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}
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else {
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return 'Typhoon detected.';
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}
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}
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message = determineTyphoonIntensity(110);
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console.log(message);
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/*
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- We can further control the flow of our program based on conditions and changing variables and results
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- The initial value of "message" was "No message."
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- Due to the conditional statements created in the function, we were able to reassign it's value and use it's new value to print a different output.
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- console.warn() is a good way to print warnings in our console that cold help us developers act on certain output within our code
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*/
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if (message == 'Tropical storm detected.') {
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console.warn(message);
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}
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// [SECTION] Truthy and Falsy
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// -In Javascript a "truthy" value is a value that is considered true when ecnountered in a Boolean context
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// - Values are considered true unless defined otherwise
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// - Falsy values/exceptions for truthy:
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/*
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1. false
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2. 0
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3. -0
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4. ""
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5. null
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6. undefined
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7. NaN
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*/
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// Truthy Examples
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// - If the result of an expression in a condition results to a truthy value, the condition retunrs true and the corresponding statements are executed
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// - Expressions are any unit of code that can bve evaluated to a value
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if (true) {
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console.log('Truthy');
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}
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if(1) {
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console.log('Truthy');
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}
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if ([]) {
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console.log('Truthy');
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}
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// Falsy examples
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if (false) {
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console.log('Falsy');
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}
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if (0) {
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console.log('Falsy');
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}
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if (undefined) {
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console.log('Falsy');
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}
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// [SECTION] Conditional (Ternary) Operator
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/*
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- The Conditional (Ternary) Operator takes in three operands:
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- 1. condition
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2. expression to execute if the condition is truthy
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3. expression to execute if the condition is falsy
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- it can be used as an alternative to an "if else" statement
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-Ternary operators have an implicit "return" statement meaning that without the return keyword, the resulting expressions can be stored in a variable.
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- It is commonly used for single statement execution.
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*/
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// Single statement execution
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let ternaryResult = (1 < 18) ? true : false;
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console.log("Result of Ternary Operator " + ternaryResult);
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// Multiple statement execution
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/*Both functions perform two seperate tasks which changes the value of the "name" variable and returns the result storing it in the "legalAge"
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*/
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let name;
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function isOflegalAge() {
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name = 'John';
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return 'You are of the legal age limit';
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}
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function isUnderAge() {
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name = 'Jane';
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return 'You are under the age limit';
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}
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let age = parseInt(prompt("What is your age?"));
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console.log(age);
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let legalAge = (age > 18) ? isOflegalAge() : isUnderAge();
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console.log("Result of Ternary Operator in functions: " + legalAge + ', ' + name);
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// [SECTION] Switch Statement
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let day = prompt("What day of the week is it today?").toLowerCase();
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console.log(day);
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switch (day) {
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case 'monday':
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console.log("The color of the day is red");
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break;
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case 'tuesday':
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console.log("The color of the day is orange");
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break;
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case 'wednesday':
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console.log("The color of the day is yellow");
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break;
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case 'thursday':
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console.log("The color of the day is green");
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break;
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case 'friday':
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console.log("The color of the day is blue");
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break;
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case 'saturday':
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console.log("The color of the day is indigo");
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break;
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case 'sunday':
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console.log("The color of the day is violet");
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break;
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default:
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console.log("Please input a valid day");
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break;
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}
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// [SECTION] Try-Catch-Finally Statement
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function showIntensityAlert(windSpeed) {
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try {
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alerat(determineTyphoonIntensity(windSpeed));
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} catch (error) {
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console.log(typeof error);
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console.warn(error.message);
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} finally {
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alert('Intensity updates will show new alert.');
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}
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}
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showIntensityAlert(56);
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