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This article mainly introduces "how to use the for loop in JavaScript". In the daily operation, I believe that many people have doubts about how to use the for loop in JavaScript. The editor consulted all kinds of materials and sorted out a simple and easy-to-use method of operation. I hope it will be helpful to answer the doubt of "how to use the for loop in JavaScript". Next, please follow the editor to study!

There are for loops in JavaScript. The for loop in the JavaScript language is used to execute code blocks multiple times. It is a loop tool commonly used in JS and is suitable for use when the number of loops is known; the syntax "for (initialization expression; conditional expression; variable update) {code executed when the conditional expression is true".

The operating environment of this tutorial: windows7 system, javascript1.8.5 version, Dell G3 computer.

There are for loops in JavaScript.

The for loop in the JavaScript language is used to execute code blocks multiple times. It is the most commonly used loop tool in JavaScript and can also be used for array traversal loops, and so on.

Why do we use for loops? For example, for example, we want the console to output all the numbers between 1 and 1000. If we write the output statement alone, we have to write 1000 lines of code, but if we use the for loop, a few sentences of code can be achieved. In short, using a for loop makes it easier and faster for us to write code (otherwise, of course, why would we want it).

JS for loop syntax

JS for loops are suitable for use when the number of loops is known, and the syntax format is as follows:

For (initialization expression; conditional expression; variable update) {/ / Code executed when the conditional expression is true

Initialization expression: usually used to declare the initial value of a counter, that is, the value at the beginning of the loop.

Conditional expression: defines the condition under which the loop block of code is run, which controls whether the code in the body of the loop is executed, and exits the loop immediately if the condition is FALSE.

Variable update: the loop code block is executed after each execution; each time the loop is executed, the value of the counter is modified immediately

The execution flow of the for loop statement is shown in the following figure:

Example 1:

For example, in a HTML file, we write the following code to calculate the sum of 1 to 100:

Var result = 0; for (var I = 1; I

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