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Mastering JavaScript Control Structures: if, else, switch, and loop Syntax Explained

This resource delves into essential JavaScript control structures, focusing on `if`, `else`, and `switch` statements, along with loops like `while` and `for`. You'll learn the syntax and see practical examples that demonstrate how to execute code conditionally and iterate through loops. Discover how to display messages based on time, process days of the week, and importantly, understand JavaScript's case sensitivity and whitespace usage. This guide is perfect for developers looking to solidify their foundations in JavaScript programming.

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Mastering JavaScript Control Structures: if, else, switch, and loop Syntax Explained

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  1. CIS 375—Web App Dev II JavaScript II

  2. if and if…else Syntax if (condition) { code to be executed if condition is true } if (condition) { code to be executed if condition is true } else { code to be executed if condition is true }

  3. Example of if Statement // Display “Good morning” if before 10 am var today = new Date() var time = today.getHours() if (time < 10) { document.write("<b>Good morning</b>") }

  4. Example of if…else Statement // Display “Good morning” if before 10 am // Display “Good day!” otherwise var today = new Date() var time = today.getHours() if (time < 10) { document.write("<b>Good morning</b>") } else { document.write("Good day!") }

  5. Syntax of switch Statement switch (expression) { case label1: code to be executed if expression = label1 break case label2: code to be executed if expression = label2 break default: code to be executed if expression is different from both label1 and label2 }

  6. Example of switch Statement var today = new Date() theDay = today.getDay() switch (theDay) { case 5: document.write("Finally Friday") break case 6: document.write("Super Saturday") break case 0: document.write("Sleepy Sunday") break default: document.write(“Can’t wait till the weekend!”) }

  7. Syntax for Looping • while while (condition) { code to be executed } • do…while do { code to be executed } while (condition) • for (equivalent to _______ with a counter variable) for (initialization; condition; increment) { code to be executed }

  8. Examples of while & do…while • while i = 0 while (i <= 5){ document.write("The number is " + i) document.write("<br>") i++ } • do…while i = 0 do{ document.write("The number is " + i) document.write("<br>") i++ } while (i <= 5)

  9. Example of for Loop for (i = 1; i <= 6; i++){ document.write("<h" +i+ ">This is header " + i) document.write("</h" + i + ">") }

  10. Miscellaneous Guidelines • JavaScript is ______ sensitive • A function named "myfunction" is not the same as "myFunction". • White space (use to make code more ___________) • JavaScript ignores extra spaces • name="Hege" same as name = "Hege“ • Use the “\” to insert special characters • document.write (“Let’s sing \"Happy Birthday\".") • Comments • Use // for single line, /*comments */ for a block

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