Mastering JavaScript

JavaScript Primer
The following example shows you how to type cast using Booleans:
const age = 0; // bad
const hasAge = new Boolean(age); // good
const hasAge = Boolean(age); // good
const hasAge = !!age;
Conditional evaluation
There are various stylistic guidelines around conditional statements. Let's study the
following code:
// When evaluating that array has length,
// WRONG:
if ( array.length > 0 ) ...
// evaluate truthiness(GOOD):
if ( array.length ) ...
// When evaluating that an array is empty,
// (BAD):
if ( array.length === 0 ) ...
// evaluate truthiness(GOOD):
if ( !array.length ) ...
// When checking if string is not empty,
// (BAD):
if ( string !== "" ) ...
// evaluate truthiness (GOOD):
if ( string ) ...
// When checking if a string is empty,
// BAD:
if ( string === "" ) ...
// evaluate falsy-ness (GOOD):
if ( !string ) ...
// When checking if a reference is true,
// BAD:
if ( foo === true ) ...
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