JavaScript 中 == 和 === 的区别

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:

• 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 ofcharacters, same length, and samecharacters in corresponding positions.
• Two numbers are strictly equal when they are numerically equal (havethe same number value). NaN is notequal to anything, including NaN.Positive and negative zeros are equalto one another.
• Two Boolean operands are strictly equal if both are true orboth 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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