150 lines
1.9 KiB
Markdown
150 lines
1.9 KiB
Markdown
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## Operators and Aliases
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Because the `==` operator frequently causes undesirable coercion, is intransitive, and has a different meaning than in other languages, CoffeeScript compiles `==` into `===`, and `!=` into `!==`. In addition, `is` compiles into `===`, and `isnt` into `!==`.
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You can use `not` as an alias for `!`.
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For logic, `and` compiles to `&&`, and `or` into `||`.
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Instead of a newline or semicolon, `then` can be used to separate conditions from expressions, in **while**, **if**/**else**, and **switch**/**when** statements.
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As in [YAML](http://yaml.org/), `on` and `yes` are the same as boolean `true`, while `off` and `no` are boolean `false`.
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`unless` can be used as the inverse of `if`.
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As a shortcut for `this.property`, you can use `@property`.
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You can use `in` to test for array presence, and `of` to test for JavaScript object-key presence.
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To simplify math expressions, `**` can be used for exponentiation and `//` performs integer division. `%` works just like in JavaScript, while `%%` provides [“dividend dependent modulo”](http://en.wikipedia.org/wiki/Modulo_operation):
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```
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codeFor('modulo')
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```
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All together now:
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<table class="definitions">
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<tbody>
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<tr>
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<th>CoffeeScript</th>
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<th>JavaScript</th>
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</tr>
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<tr>
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<td>`is`</td>
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<td>`===`</td>
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</tr>
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<tr>
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<td>`isnt`</td>
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<td>`!==`</td>
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</tr>
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<tr>
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<td>`not`</td>
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<td>`!`</td>
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</tr>
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<tr>
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<td>`and`</td>
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<td>`&&`</td>
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</tr>
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<tr>
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<td>`or`</td>
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<td>`||`</td>
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</tr>
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<tr>
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<td>`true`, `yes`, `on`</td>
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<td>`true`</td>
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</tr>
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<tr>
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<td>`false`, `no`, `off`</td>
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<td>`false`</td>
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</tr>
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<tr>
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<td>`@`, `this`</td>
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<td>`this`</td>
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</tr>
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<tr>
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<td>`of`</td>
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<td>`in`</td>
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</tr>
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<tr>
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<td>`in`</td>
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<td>_<small>no JS equivalent</small>_</td>
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</tr>
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<tr>
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<td>`a ** b`</td>
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<td>`Math.pow(a, b)`</td>
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</tr>
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<tr>
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<td>`a // b`</td>
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<td>`Math.floor(a / b)`</td>
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</tr>
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<tr>
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<td>`a %% b`</td>
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<td>`(a % b + b) % b`</td>
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</tr>
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</tbody>
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</table>
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```
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codeFor('aliases')
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```
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