22.1 Perform type coercion at the beginning of the statement.
22.2 Strings:
// => this.reviewScore = 9;
// bad
const totalScore = this.reviewScore + ''; // invokes this.reviewScore.valueOf()
// bad
const totalScore = this.reviewScore.toString(); // isn’t guaranteed to return a string
// good
const totalScore = String(this.reviewScore);
22.3 Numbers: Use Number for type casting and parseInt always with a radix for parsing strings. eslint: radix
const inputValue = '4';
// bad
const val = new Number(inputValue);
// bad
const val = +inputValue;
// bad
const val = inputValue >> 0;
// bad
const val = parseInt(inputValue);
// good
const val = Number(inputValue);
// good
const val = parseInt(inputValue, 10);
22.4 If for whatever reason you are doing something wild and parseInt is your bottleneck and need to use Bitshift for performance reasons, leave a comment explaining why and what you’re doing.
// good
/**
* parseInt was the reason my code was slow.
* Bitshifting the String to coerce it to a
* Number made it a lot faster.
*/
const val = inputValue >> 0;
22.5 Note: Be careful when using bitshift operations. Numbers are represented as 64-bit values, but bitshift operations always return a 32-bit integer (source). Bitshift can lead to unexpected behavior for integer values larger than 32 bits. Discussion. Largest signed 32-bit Int is 2,147,483,647:
2147483647 >> 0; // => 2147483647
2147483648 >> 0; // => -2147483648
2147483649 >> 0; // => -2147483647
22.6 Booleans:
const age = 0;
// bad
const hasAge = new Boolean(age);
// good
const hasAge = Boolean(age);
// best
const hasAge = !!age;