什么是顶级的JavaScript陷阱？

问题描述

我知道，我知道，我知道我的这个故事，在我完全理解关闭之前，有几个问题，但JavaScript中的很多奇怪的行为并不是我想到的...

那么哪个陷阱应该你肯定会指出新秀？

解决方案

。

 ''=='0' // false 
 0 ==''// true 
 0 =='0'// true 
 false =='false'// false 
 false =='0 '// true 
 false == undefined // false 
 false == null // false 
 null == undefined // true 
\t\r\ n= = 0 // true 
  

以及 null 和未定义。如上表所列，比较 null & 未定义与 == 返回true，但使用 === 它返回false。一旦您明白 undefined 与具有 null 值的变量有很大的不同，那么这个行为是有道理的，

I'm planing on giving an introduction talk on JavaScript and in the preparation process I wondered what the top pitfalls are that rookies fall into.

I know I've had a few gotchas before I fully understood closure, but much of the strange behavior in JavaScript is not something I think about any more...

So, which pitfalls should you definitely point out to the rookies?

解决方案

Boolean type conversion.

''        ==   '0'           //false
0         ==   ''            //true
0         ==   '0'           //true
false     ==   'false'       //false
false     ==   '0'           //true
false     ==   undefined     //false
false     ==   null          //false
null      ==   undefined     //true
" \t\r\n" ==   0             //true

As well as the difference between null and undefined. As listed in the table above, comparing null & undefined with == returns true, but with === it returns false. This behavior makes sense once you understand that undefined is very different from a variable having a null value, and something holding the value undefined is different from something being undefined.

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