How to understand the equivalence comparison in javascript
This article introduces the relevant knowledge of "how to understand the equivalence in javascript". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!
Equivalent comparison refers to comparing whether the values of two expressions (or operands) are equal, the comparison methods are: 1, the use of the "= =" operator, the syntax "Object.is (a, b)"; 2, the use of the "= =" operator, the syntax "Object.is (a, b)".
The operating environment of this tutorial: windows7 system, javascript1.8.5 version, Dell G3 computer.
Equivalent comparison in javascript
In javascript, equivalence comparison refers to comparing whether the values of two expressions (or operands) are equal.
We all know that JavaScript is a loose type, and in some cases, when using = = for equivalence comparisons, it can give you unexpected results. This is because JavaScript implicitly casts the values of the two comparisons when using = = for an equivalent comparison.
0 = ='/ / truenull = = undefined / / true [1] = = true / / true
So JavaScript also provides us with three equal sign operators, which are stricter and do not cast comparisons, but practical = = comparisons are sometimes not the best solution:
NaN = NaN / / false
The good news is that there is a new, better and more accurate method in ES6, Object.is (), which has the same functionality as = = and performs well in some special cases:
Object.is (0,'); / / falseObject.is (null, undefined); / / falseObject.is ([1], true); / / falseObject.is (NaN, NaN); / / true
The following figure illustrates in detail the similarities and differences of the equivalent price comparison between =, and Object.is ():
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