Invert an object, such that keys become values and values become keys.
We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we’ve built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.
The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.
When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.
To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
Invert an object, such that keys become values and values become keys.
bash
npm install @stdlib/utils-object-inversescript tag without installation and bundlers, use the [ES Module][es-module] available on the [esm][esm-url] branch (see [README][esm-readme]).deno][deno-url] branch (see [README][deno-readme] for usage intructions).umd][umd-url] branch (see [README][umd-readme]).javascript
var invert = require( '@stdlib/utils-object-inverse' );object, such that keys become values and values become keys.javascript
var out = invert({
'a': 'beep',
'b': 'boop'
});
// returns { 'beep': 'a', 'boop': 'b' }options:boolean indicating whether to store keys mapped to duplicate values in arrays. Default: true.arrays.javascript
var out = invert({
'a': 'beep',
'b': 'beep'
});
// returns { 'beep': [ 'a', 'b' ] }duplicates option to false. The output key-value pair will be the key most recently inserted into the input object.javascript
var obj = {};
obj.a = 'beep';
obj.b = 'boop';
obj.c = 'beep'; // inserted after `a`
var out = invert( obj, {
'duplicates': false
});
// returns { 'beep': 'c', 'boop': 'b' }objects having values which are themselves objects. This implementation relies on native object serialization (#toString) when converting values to keys.javascript
var obj = {
'a': [ 1, 2, 3 ],
'b': {
'c': 'd'
}
};
var out = invert( obj );
// returns { '1,2,3': 'a', '[object Object]': 'b' }object key enumeration is not specified according to the [ECMAScript specification][ecma-262-for-in]. In practice, however, most engines use insertion order to sort an object‘s keys, thus allowing for deterministic inversion.javascript
var randu = require( '@stdlib/random-base-randu' );
var round = require( '@stdlib/math-base-special-round' );
var invert = require( '@stdlib/utils-object-inverse' );
var keys;
var arr;
var out;
var i;
// Create an array of random integers...
arr = new Array( 1000 );
for ( i = 0; i < arr.length; i++ ) {
arr[ i ] = round( randu()*100.0 );
}
// Invert the array to determine value frequency...
out = invert( arr );
keys = Object.keys( out );
for ( i = 0; i < keys.length; i++ ) {
if ( out[ i ] ) {
out[ i ] = out[ i ].length;
} else {
out[ i ] = 0;
}
}
console.dir( out );
