立即执行函数(immediate)的原理

immediate与debounce相似，immediat连续执行，且间隔不超过500ms，lazyLoad只执行一次，不同于immediate的是现在lazyLoad会先执行，

var safe=true;
function immediate() {
        if (safe) {
 	    lazyLoad();
            	    safe = false;
        }
        clearTimeout(timer);
        timer = setTimeout(function() {
            	    safe = true;
        }, 500);
}

demo-immediate：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body style="height:2000px">
<script>

    /*immediate与debounce相似， immediat连续执行，且间隔不超过500ms，
     srollFn 只执行一次，不同的是srollFn 会先执行*/



    var num=0;
    function lazyLoad() {
        num++;
        console.log(num);
    }

    var timer = null;
    var safe=true;
    function immediate() {
        if (safe) {
            lazyLoad();
            safe = false;
        }
        clearTimeout(timer);
        timer = setTimeout(function() {
            safe = true;
        }, 1000);
    }
    window.onscroll = immediate;



</script>
</body>
</html>

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原文地址：https://www.cnblogs.com/aredleave/p/7573155.html