jiff/lib/array.js

JSON diff and patch based on rfc6902

/** @license MIT License (c) copyright 2010-2014 original author or authors */
/** @author Brian Cavalier */
/** @author John Hann */

exports.cons = cons;
exports.tail = tail;
exports.map = map;

/**
 * Prepend x to a, without mutating a. Faster than a.unshift(x)
 * @param {*} x
 * @param {Array} a array-like
 * @returns {Array} new Array with x prepended
 */
function cons(x, a) {
	var l = a.length;
	var b = new Array(l+1);
	b[0] = x;
	for(var i=0; i<l; ++i) {
		b[i+1] = a[i];
	}

	return b;
}

/**
 * Create a new Array containing all elements in a, except the first.
 *  Faster than a.slice(1)
 * @param {Array} a array-like
 * @returns {Array} new Array, the equivalent of a.slice(1)
 */
function tail(a) {
	var l = a.length-1;
	var b = new Array(l);
	for(var i=0; i<l; ++i) {
		b[i] = a[i+1];
	}

	return b;
}

/**
 * Map any array-like. Faster than Array.prototype.map
 * @param {function} f
 * @param {Array} a array-like
 * @returns {Array} new Array mapped by f
 */
function map(f, a) {
	var b = new Array(a.length);
	for(var i=0; i< a.length; ++i) {
		b[i] = f(a[i]);
	}
	return b;
}