這是一段聲稱(chēng)7位數(shù)隨機(jī)數(shù)的代碼;當(dāng)var arr =? [ ];? var newArr = [ ]; 這兩個(gè)變量為全局變量的時(shí)候，每次觸發(fā)點(diǎn)擊事件，oDiv.innerHTML的結(jié)果都會(huì)在頁(yè)面累加；但是當(dāng)這兩個(gè)變量為函數(shù)局部變量的時(shí)候，每次就可以只正常顯示7個(gè)隨機(jī)數(shù)。請(qǐng)大神解惑，謝謝啦~<!DOCTYPE html><html><head>??? <meta charset="utf-8">?? ?<title></title>?? ?<script type="text/javascript">?? ?window.onload=function(){??????? //獲取元素input?? ??? ?var oBtn = document.getElementById('btn');?? ??? ?//獲取元素div?? ??? ?var oDiv = document.getElementById('div1');?? ??? ?//聲明兩個(gè)空數(shù)組?? ??? ?/*var arr = [];?? ??? ?var newArr = [];*/?? ??? ?//給按鈕添加事件，執(zhí)行函數(shù)randomNum。?? ??? ?oBtn.onclick = function(){?? ??? ??? ?oDiv.innerHTML = randomNum(35,7);?? ??? ?};?? ??? ?function randomNum(iAll,iNum){?? ??? ??? ?var arr = [];?? ??? ??? ?var newArr = [];?? ??? ??? ?for(var i=1;i<=iAll;i++){?? ??? ??? ??? ?arr.push(i); //? arr：1~35?? ??? ??? ?}?? ??? ??? ?for(var i=1;i<=iNum;i++){?? ??? ??? ??? ?//獲取7個(gè)隨機(jī)數(shù)?? ??? ??? ??? ?var num = arr.splice(Math.floor(Math.random()*arr.length),1);?? ??? ??? ??? ??? ??? ?newArr.push(num);?? ??? ??? ??? ?}?? ??? ??? ?//返回包含7個(gè)隨機(jī)數(shù)的數(shù)組?? ??? ??? ?return newArr;?? ??? ?};?? ?};?? ?</script></head><body><input id="btn" type="button" value="生成隨機(jī)數(shù)"><div id="div1"></div></body></html>
關(guān)于javascript變量作用域的問(wèn)題
夏天的夏7
2016-12-06 10:12:04