Summary of for loop usage in javascript_Basic knowledge

The most commonly used one is for (initial value of loop variable; loop condition; increment value) {statement;}
Example

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The following are other usages
(1) Omit expression 1. At this time, the loop variable should be assigned an initial value before the for statement. Pay attention to the following; cannot be omitted.
Example:

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(2) Omit expression 2, that is, the loop condition loop continues without termination, that is, expression 2 is always true.

Example:

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(3) Omit expression 3. But you need to ensure that the cycle can end normally

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](4) Omit expression 1, 3

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This is equivalent to while , you can use for instead of while.
(5) All three expressions are omitted

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]This loop will never terminate Carry out the same function of small while(true){}.
(6) Expression 1 can be the initial value of the loop variable, or it can be other expressions unrelated to the loop variable.

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]Expression 1 and expression 3 can also be a comma expression (containing more than one expression, separated by commas);

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逗号表达式按从左-右的顺序整个逗号表达式的值为最右边的值。

<script type="text/javascript"> for(i=0;i<100;i++,i++) { document.write(i); } </script>
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这个就是 

<script type="text/javascript"> for(i=0;i<100;i+=2) { document.write(i); } </script>
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(7) 表达式可以是逻辑表达式，字符表达式，只要非false就可以执行循环 

<script> n=confirm("FOR") for(;n;) { document.write("hello"); } </script>
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从这些可以看到for与while循环比起来功能很强大.