JavaScript 的 == 條列式比較

出自規格書裡面的「7.2.14 Abstract Equality Comparison」,我都是遇到再去查,不過如果有人想要理解與背起來的,可以參考這邊:「JavaScript "loose" comparison step by step」。

The comparison x == y, where x and y are values, produces true or false. Such a comparison is performed as follows:

If Type(x) is the same as Type(y), then
Return the result of performing Strict Equality Comparison x === y.
If x is null and y is undefined, return true.
If x is undefined and y is null, return true.
If Type(x) is Number and Type(y) is String, return the result of the comparison x == ! ToNumber(y).
If Type(x) is String and Type(y) is Number, return the result of the comparison ! ToNumber(x) == y.
If Type(x) is Boolean, return the result of the comparison ! ToNumber(x) == y.
If Type(y) is Boolean, return the result of the comparison x == ! ToNumber(y).
If Type(x) is either String, Number, or Symbol and Type(y) is Object, return the result of the comparison x == ToPrimitive(y).
If Type(x) is Object and Type(y) is either String, Number, or Symbol, return the result of the comparison ToPrimitive(x) == y.
Return false.

這邊方便的點在於給了網頁操作,在看半天不知道為什麼時,可以看出是哪條規則跟自己理解不同...

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  1. Pingback: YAML 的痛點 – Gea-Suan Lin's BLOG

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