Coercion in javascript?

JavaScript
1

In the below code coercion is happening alright , but == operators need booleans to compare so coerced string potato will return true , then true == true it has to return true right but why its returning false.

 console.log("potato" == true);  //false
2

That’s an incorrect assumption. When you check the ECMAScript specification, you’ll find a whole different algorithm: (cf. https://www.ecma-international.org/ecma-262/6.0/index.html#sec-abstract-equality-comparison)

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

1. ReturnIfAbrupt(x).
2. ReturnIfAbrupt(y).
3. If Type(x) is the same as Type(y), then
    Return the result of performing Strict Equality Comparison x === y.
4. If x is null and y is undefined, return true.
5. If x is undefined and y is null, return true.
6. If Type(x) is Number and Type(y) is String,
    return the result of the comparison x == ToNumber(y).
7. If Type(x) is String and Type(y) is Number,
    return the result of the comparison ToNumber(x) == y.
8. If Type(x) is Boolean, return the result of the comparison ToNumber(x) == y.
9. If Type(y) is Boolean, return the result of the comparison x == ToNumber(y).
10. If Type(x) is either String, Number, or Symbol and Type(y) is Object, then
    return the result of the comparison x == ToPrimitive(y).
11. If Type(x) is Object and Type(y) is either String, Number, or Symbol, then
    return the result of the comparison ToPrimitive(x) == y.
12. Return false.

For your case step 9 is applied ( 'potato' == 1), and subsequently step 7 ( NaN == 1) and step 3 (NaN === 1).

1 Like
3

Ok.i got it

4

The trouble with understanding double equals is why the triple equals was invented. Best practice is to just use triple equals to prevent all of the confusion from happening.

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5

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