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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 theToBoolean
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.