mungedb-aggregate/lib/pipeline/expressions/SetDifferenceExpression.js

"use strict";

/**
 * A $setdifference pipeline expression.
 * @see evaluateInternal
 * @class SubstrExpression
 * @namespace mungedb-aggregate.pipeline.expressions
 * @module mungedb-aggregate
 * @constructor
 **/
var SetDifferenceExpression = module.exports = function SetDifferenceExpression() {
		this.fixedAirty(2);
		if (arguments.length !== 2) throw new Error("two args expected");
		base.call(this);
}, klass = SetDifferenceExpression,
		base = require("./NaryExpression"),
		proto = klass.prototype = Object.create(base.prototype, {
				constructor: {
						value: klass
				}
		});

// DEPENDENCIES
var Value = require("../Value"),
		Expression = require("./Expression");

// PROTOTYPE MEMBERS
proto.getOpName = function getOpName() {
		return "$setdifference";
};

/**
 * Takes 2 arrays. Assigns the second array to the first array.
 * @method evaluateInternal
 **/
proto.evaluateInternal = function evaluateInternal(doc) {
		var array1 = this.operands[0].evaluateInternal(doc),
				array2 = this.operands[1].evaluateInternal(doc);
		if (array1 instanceof Array) throw new Error(this.getOpName() + ": object 1 must be an array");
		if (array2 instanceof Array) throw new Error(this.getOpName() + ": object 2 must be an array");

		var returnVec = [];

		array1.forEach(function(key) {
				if (-1 === array2.indexOf(key)) {
						returnVec.push(key);
				}
		}, this);
		return returnVec;
};

/** Register Expression */
Expression.registerExpression("$setdifference", SetDifferenceExpression.parse);