javascript difference between == and ===

最新推荐文章于 2023-07-04 14:05:31 发布

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本文详细介绍了JavaScript中严格的和类型转换的相等性比较。包括字符串、数值、布尔值及对象之间的比较规则，并通过实例展示了如何进行相等性判断。

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JavaScript has both strict and type-converting equality comparison. For strict equality the objects being compared must have the same type and:
Two strings are strictly equal when they have the same sequence of characters, same length, and same characters in corresponding positions.
Two numbers are strictly equal when they are numerically equal (have the same number value). NaN is not equal to anything, including NaN. Positive and negative zeros are equal to one another.
Two Boolean operands are strictly equal if both are true or both are false.
Two objects are strictly equal if they refer to the same Object.
Null and Undefined types are == (but not ===).
0==false   // true
0===false  // false, because they are of a different type
1=="1"     // true, auto type coersion
1==="1"    // false, because they are of a different type
>>> new String("aa")===new String("aa")

false

>>> new String("aa")==new String("aa")

false

>>> "aa"=="aa"

true

>>> "aa"==="aa"

true

>>> NaN===NaN //false
>>> var user1 = {name : "nerd", org: "dev"}; var user2 = {name : "nerd", org: "dev"}; console.log(user1==user2)

false
For furthur information, please check
http://stackoverflow.com/questions/1068834/object-comparison-in-javascript