Comparison Operators & Equality Back

• use === or !== rather than == or !=

1. Conditional statements

• Conditional statements such as the if statement evaluate their expression using coericion(強制多態) with the ToBoolean abstract method and always follow these simple rules:
• Eslint rules tags: eqeqeq
  • Objects evaluate to true.
  • Undefined evaluate to false.
  • Null evaluate to false.
  • Booleans evaluate to the value of the boolean
  • Numbers evaluate to false if +0, -0, or Nan, otherwise true
  • Strings evaluate to false if an empty string '', otherwise true.

if ([false]) {
    /**
     * true
     * because this is an object
     */
}

2. Use shortcuts

/**
 * bad
 */
if (name !== '') {
    /**
     * ...
     */
}

/**
 * good
 */
if (name) {
    /**
     * ...
     */
}

/**
 * bad
 */
if (collections.length > 0) {
    /**
     * ...
     */
}

/**
 * good
 */
if (collections.length) {
    /**
     * ...
     */
}

3. More details

• Truth Equality and JavaScript by Angus Croll.