对于(;;)循环说明 [英] For (;;) loop explanation

问题描述

在JS中，我偶然发现了一种for循环，该循环是 for(;;)，其功能类似于 while(true)循环.分号在此for循环的括号中起什么作用?

In JS I stumbled across a kind of for loop which is for(;;) that functions like a while(true) loop. What do the semicolons function in the brackets of this for loop?

推荐答案

for (statement 1; statement 2; statement 3) {
    code block to be executed
}

语句1是可选的，并且在循环(代码块)开始之前执行.

Statement 1 is optional and is executed before the loop (the code block) starts.

var i = 0;
var length = 10
for (; i < length; i++) { 

    //The for loop run until i is less than length and you incerement i by 1 each time. javascript doesnt care what you do inside, it just check whether you have variable with name i and length
}

语句2也是可选的，它定义了运行循环(代码块)的条件.

Statement 2 is again optional defines the condition for running the loop (the code block).

var i = 0;
var len = 100;
for (i = 5; ; i++) { 
    //Here you are just initializing i with 5 and increment it by 1 there is no break condition so this will lead to an infinite loop hence we should always have a break here somehwere.
}

语句3是可选的，并且在每次执行循环(代码块)之后都会执行.

Statement 3 is optional and is executed each time after the loop (the code block) has been executed.

var i = 0;
var length = 100;
for (; i < length; ) { 
    //Here you are just checking for i < length which is true. If you don't increment i or have an break it will turn into infinite loop
}

在坚果壳中，如果没有条件或没有初始化，它将变成无限循环.

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