ifnotundef

ifnotundef

     A set of helper functions that simplify the (is a undefined ? b : c) syntax

Author: Loïc Formont
License: MIT Licensed
Example
``javascript var undef = require("ifnotundef"); `

* ifnotundef
[.if(a, b, [c])](#module_ifnotundef.if) ⇒ \
* .is(a, b) ⇒ boolean
* .isnot(a, b) ⇒ boolean
* .check(a, b) ⇒ boolean
[.try(a, [b])](#module_ifnotundef.try) ⇒ \
[.child(a, b, c, [d])](#module_ifnotundef.child) ⇒ \

$3

Two parameters mode If a is undefined, return b else a Three parameters mode If a is undefined, return c else b

Kind: static method of ifnotundef
Returns: \* - a, b or c depending on their undefined status

| Param | Type | Description |
| --- | --- | --- |
| a | \* | the first parameter |
| b | \* | the second parameter |
| [c] | \* | the third parameter |

Example
Two ways to use if. Either with two parameters (a||b): `javascript var myHost = undef.if(options.host, options.hostname); ` or with three parameters (a?b:c): `javascript var myHost = undef.if(options.host, options.hostname, 'localhost'); `


$3

Invert of "check"

Kind: static method of ifnotundef
Returns: boolean - a or a[b]'s undefined status

| Param | Type | Description |
| --- | --- | --- |
| a | \* | the variable to check |
| b | \* | the child path |

Example
`javascript if(undef.is(options.host)) console.log('Deal with it'); `


$3

Alias of "check"

Kind: static method of ifnotundef
Returns: boolean - a or a[b]'s undefined status

| Param | Type | Description |
| --- | --- | --- |
| a | \* | the variable to check |
| b | \* | the child path |

Example
`javascript if(undef.isnot(options.host)) console.log('Great'); `


$3

One parameters mode If a is undefined, false else true Two parameters mode If a[b] is undefined, false else true

Kind: static method of ifnotundef
Returns: boolean - a or a[b]'s undefined status

| Param | Type | Description |
| --- | --- | --- |
| a | \* | the variable to check |
| b | \* | the child path |

Example
`javascript if(!undef.check(options.host)) console.log('Deal with it'); `


$3

One parameters mode If a is undefined, throw a else return a Two parameters mode If a is undefined, throw b else return a

Kind: static method of ifnotundef
Returns: \* - a or exception depending on a's undefined status

| Param | Type | Description |
| --- | --- | --- |
| a | \* | the parameter to try |
| [b] | \* | the error message |

Example
Two ways to use if. Either with one parameter: `javascript var myHost = undef.try(options.host); ` or with two parameters: `javascript var myUndefined = undef.try(undefined, 'undefined is not defined ... ;-)'); // Exeption raised above `


$3

Three parameters mode If a[b] is undefined, return c else a[b] Four parameters mode If a[b] is undefined, return d else c

Kind: static method of ifnotundef
Returns: \* - a[b] or c or d depending on their undefined status

| Param | Type | Description |
| --- | --- | --- |
| a | \* | the object |
| b | \* | the child path |
| c | \* | the first value |
| [d] | \* | the second value |

Example
Two ways to use child. Either with three parameters (a[b]||c): `javascript var myHost = undef.child(options, ['params', 'host'], 'localhost'); ` or with four parameters (a[b]?c:d): `javascript var myHost = undef.child(options, ['params'], options.params.host, 'localhost'); ``