Loops can execute a block of code a number of times. Show JavaScript LoopsLoops are handy, if you want to run the same code over and over again, each time with a different value. Often this is the case when working with arrays: Instead of writing: text += cars[0] + "<br>"; You can write: for (let i = 0; i < cars.length; i++) { Try it Yourself » Different Kinds of LoopsJavaScript supports different kinds of loops:
The For LoopThe for (expression 1; expression 2; expression 3) { Expression 1 is executed (one time) before the execution of the code block. Expression 2 defines the condition for executing the code block. Expression 3 is executed (every time) after the code block has been executed. Example for (let i = 0; i < 5; i++) { Try it Yourself » From the example above, you can read: Expression 1 sets a variable before the loop starts (let i = 0). Expression 2 defines the condition for the loop to run (i must be less than 5). Expression 3 increases a value (i++) each time the code block in the loop has been executed. Expression 1Normally you will use expression 1 to initialize the variable used in the loop (let i = 0). This is not always the case. JavaScript doesn't care. Expression 1 is optional. You can initiate many values in expression 1 (separated by comma): Example for (let i = 0, len = cars.length, text = ""; i < len; i++) { Try it Yourself » And you can omit expression 1 (like when your values are set before the loop starts): Example let i = 2; Try it Yourself » Expression 2Often expression 2 is used to evaluate the condition of the initial variable. This is not always the case. JavaScript doesn't care. Expression 2 is also optional. If expression 2 returns true, the loop will start over again. If it returns false, the loop will end. If you omit expression 2, you must provide a break inside the loop. Otherwise the loop will never end. This will crash your browser. Read about breaks in a later chapter of this tutorial. Expression 3Often expression 3 increments the value of the initial variable. This is not always the case. JavaScript doesn't care. Expression 3 is optional. Expression 3 can do anything like negative increment (i--), positive increment (i = i + 15), or anything else. Expression 3 can also be omitted (like when you increment your values inside the loop): Example let i = 0; Try it Yourself » Loop ScopeUsing Examplevar i = 5; for (var i = 0; i < 10; i++) { // Here i is 10 Try it Yourself » Using Examplelet i = 5; for (let i = 0; i < 10; i++) { // Here i is 5 Try it Yourself » In the first example, using In the second example, using When For/Of and For/In LoopsThe While LoopsThe How do you write a for loop in HTML using JavaScript?From the example above, you can read: Expression 1 sets a variable before the loop starts (let i = 0). Expression 2 defines the condition for the loop to run (i must be less than 5). Expression 3 increases a value (i++) each time the code block in the loop has been executed.
Can you use a for loop in HTML?Approach 1: Using the for loop: The HTML elements can be iterated by using the regular JavaScript for loop. The number of elements to be iterated can be found using the length property. The for loop has three parts, initialization, condition expression, and increment/decrement expression.
How do you make a loop in HTML?HTML isn't a programming language and doesn't have the ability to write loops. To do that you will need some other language to generate HTML, e.g. JavaScript. Show activity on this post. Then you could just change i < 10 to change how many items are output.
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