1.
2
var a = 1;undefineda1alert(a);undefined
var b = true;var c = "Hi";undefinedalert(b);alert(c);undefined
function foo(bar){alert(bar);return bar;}undefinedvar z = foo("Hi");undefinedz"Hi"
function foo(bar){alert(bar);return bar;}
- shift+enter 换行
function foo(bar){if (bar > 3){alert(bar + 1);} else {alert("Not enough");}}undefinedfoo(5)undefinedfoo(2);undefined
3
var arr = []undefinedfunction foo(bar){if (bar > 3){arr.push(bar);} else {alert("Not enough");}}undefinedfoo(2);undefinedfoo(6);undefinedarr;[6]
var o = {one:1,two:2}undefinedo.one1o.two2
4
document#documentdocument.querySelector("#sidebar")<div id=?"sidebar">?…?</div>?var el = document.querySelector("#sidebar");undefinedel<div id=?"sidebar">?…?</div>?el.setAttribute("style","display:none;")undefined
5
6
2 ?js的20/80关键知识
原文地址：https://www.cnblogs.com/venicid/p/8158413.html