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- <p align="center">
- <a href="http://gulpjs.com">
- <img height="257" width="114" src="https://raw.githubusercontent.com/gulpjs/artwork/master/gulp-2x.png">
- </a>
- </p>
-
- # value-or-function
-
- [![NPM version][npm-image]][npm-url] [![Downloads][downloads-image]][npm-url] [![Build Status][travis-image]][travis-url] [![AppVeyor Build Status][appveyor-image]][appveyor-url] [![Coveralls Status][coveralls-image]][coveralls-url] [![Gitter chat][gitter-image]][gitter-url]
-
- Normalize a value or function, applying extra args to the function
-
- ## Example
-
- ```js
- var normalize = require('value-or-function');
-
- // Values matching type are returned
- var isEnabled = normalize('boolean', true);
- // isEnabled === true
-
- // Values not matching type return undefined
- var isEnabled = normalize('boolean', 1);
- // isEnabled === undefined
-
- // Functions are called
- var isEnabled = normalize('boolean', function() {
- return false;
- });
- // isEnabled === false
-
- // Extra arguments are applied to function
- var count = normalize('number', function(a, b) {
- return a + b;
- }, 1, 2);
- // count === 3
-
- // Supply the function with context
- var context = { c: 3 };
- var count = normalize.call(context, 'number', function(a, b) {
- return a + b + this.c;
- }, 1, 2);
- // count === 6
-
- // Values one of multiple types are returned
- var isEnabled = normalize(['string', 'boolean'], true);
- // isEnabled === true
-
- // Provide a function as first argument to do custom coercion
- var now = new Date();
- var enabledSince = normalize(function(value) {
- if (value.constructor === Date) {
- return value;
- }
- }, now);
- // enabledSince === now
-
- // Convenience methods are available for the built-in types
- var result = normalize.object({});
- var result = normalize.number(1);
- var result = normalize.string('');
- var result = normalize.symbol(Symbol());
- var result = normalize.boolean(true);
- var result = normalize.function(function() {});
- var result = normalize.date(new Date());
- ```
-
- ## API
-
- ### `normalize(coercer, value[, ...appliedArguments])`
-
- Takes a coercer function `coercer` to transform `value` to the desired type.
- Also optionally takes any extra arguments to apply to `value` if `value` is a function.
-
- If the return value of `coercer(value)` is not `null` or `undefined`, that value is returned.
- Otherwise, if `value` is a function, that function is called with any extra arguments
- supplied to `normalize`, and its return value is passed through the coercer.
-
- If `coercer` is a string, it must be one of the built-in types (see below)
- and the appropriate default coercer is invoked, optionally first reducing `value`
- to a primitive type with `.valueOf()` if it is an Object.
-
- If `coercer` is an array, each element is tried until one returns something other
- than `null` or `undefined`, or it results in `undefined` if all of the elements yield `null` or `undefined`.
-
- #### `normalize.object(value[, ...appliedArguments])`
-
- Convenience method for `normalize('object', ...)`.
-
- #### `normalize.number(value[, ...appliedArguments])`
-
- Convenience method for `normalize('number', ...)`.
-
- #### `normalize.string(value[, ...appliedArguments])`
-
- Convenience method for `normalize('string', ...)`.
-
- #### `normalize.symbol(value[, ...appliedArguments])`
-
- Convenience method for `normalize('symbol', ...)`.
-
- #### `normalize.boolean(value[, ...appliedArguments])`
-
- Convenience method for `normalize('boolean', ...)`.
-
- #### `normalize.function(value[, ...appliedArguments])`
-
- Convenience method for `normalize('function', ...)`.
-
- #### `normalize.date(value[, ...appliedArguments])`
-
- Convenience method for `normalize('date', ...)`.
-
- ## License
-
- MIT
-
- [downloads-image]: http://img.shields.io/npm/dm/value-or-function.svg
- [npm-url]: https://npmjs.org/package/value-or-function
- [npm-image]: http://img.shields.io/npm/v/value-or-function.svg
-
- [travis-url]: https://travis-ci.org/gulpjs/value-or-function
- [travis-image]: http://img.shields.io/travis/gulpjs/value-or-function.svg?label=travis-ci
-
- [appveyor-url]: https://ci.appveyor.com/project/gulpjs/value-or-function
- [appveyor-image]: https://img.shields.io/appveyor/ci/gulpjs/value-or-function.svg?label=appveyor
-
- [coveralls-url]: https://coveralls.io/r/gulpjs/value-or-function
- [coveralls-image]: http://img.shields.io/coveralls/gulpjs/value-or-function/master.svg
-
- [gitter-url]: https://gitter.im/gulpjs/gulp
- [gitter-image]: https://badges.gitter.im/gulpjs/gulp.png
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