onclick事件點(diǎn)擊后為什么使setTimeout(),不斷循環(huán)
<!DOCTYPE?HTML>
<html>
<head>
<script?type="text/javascript">
var?num=0;
function?numCount(){
?document.getElementById('txt').value=num;
?num=num+1;
?setTimeout("numCount()",1000);
?}
</script>
</head>
<body>
<form>
<input?type="text"?id="txt"?/>
<input?type="button"?value="Start"?/>
</form>
</body>
</html>點(diǎn)擊事件不是只執(zhí)行一次嗎，底層是怎么運(yùn)作的？
2018-06-15
setTimeout（）計(jì)時(shí)是只執(zhí)行一次numCout（）函數(shù)，但是
function?numCount(){ ?document.getElementById('txt').value=num; ?num=num+1; ?setTimeout("numCount()",1000); ?}這個(gè)函數(shù)內(nèi)部又嵌套執(zhí)行一次，這樣就一直循壞嵌套執(zhí)行下去啦。
2018-06-03
<!DOCTYPE?HTML> <html> <head> <script?type="text/javascript"> var?num=0; function?numCount(){ ?document.getElementById('txt').value=num; ?num=num+1; ?setTimeout("numCount()",1000); ?} </script> </head> <body> <form> <input?type="text"?id="txt"?/> <input?type="button"?value="Start"?onClick="numCount()"?/> </form> </body> </html>