javascript - for(;;)循环解释

Question

在 JS 中，我偶然发现了一种 for 循环，它是 for(;;)，其功能类似于 while(true) 循环。这个for循环括号里的分号有什么作用？

Answer 1

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

语句 1 是可选的，在循环(代码块)开始之前执行。

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 再次是可选的，它定义了运行循环(代码块)的条件。

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，每次在循环(代码块)执行后执行。

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
}

简而言之，当您没有条件或初始化时，它会变成无限循环。