JavaScript 中 == 和 === 的区别 [英] Difference between == and === in JavaScript

问题描述

JavaScript 中的 == 和 === 有什么区别?我还见过 != 和 !== 运算符.还有更多这样的运营商吗?

What is the difference between == and === in JavaScript? I have also seen != and !== operators. Are there more such operators?

推荐答案

=== 和 !== 是严格的比较运算符:

=== and !== are strict comparison operators:

JavaScript 有严格的和类型转换等式比较.对于 strict 相等，对象是比较必须具有相同的类型和:

JavaScript has both strict and type-converting equality comparison. For strict equality the objects being compared must have the same type and:

• 当两个字符串具有相同的序列时，它们严格相等字符，长度相同，相同对应位置的字符.
• 两个数在数值上相等时严格相等(有相同的数值).NaN 不是等于任何东西，包括 NaN.正负零相等彼此.
• 如果两个布尔操作数都为真或为真，则两个布尔操作数严格相等两者都是假的.
• 如果两个对象引用同一个Object，则它们严格相等.
• Null 和 Undefined 类型是 ==(但不是 ===).[IE.(Null==Undefined) 是 true 但 (Null==Undefined) 是 false]

• 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 ===). [I.e. (Null==Undefined) is true but (Null===Undefined) is false]

比较运算符 - MDC

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