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: If you need to introduce external Js, you need to refresh to execute
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(2) Omit expression 2, that is, the loop condition loop continues without termination, that is, expression 2 is always true. [Ctrl A Select all Note:
If you need to introduce external Js, you need to refresh to execute
]
[Ctrl A Select all Note:
If you need to introduce external Js, you need to refresh to execute

[Ctrl A Select all Note:
If you need to introduce external Js, you need to refresh it to execute
]


[Ctrl A Select all Note:
If you need to introduce external Js, you need to refresh to execute it

[Ctrl A select all Note: If you need to introduce external Js, you need to refresh to execute ]
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。

这个就是 


(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 
从这些可以看到for与while循环比起来功能很强大.