can-map.js
function () {
			this._computedAttrs = Object.create(null);

			var computes = this.constructor._computedPropertyNames;

			for (var i = 0, len = computes.length; i < len; i++) {
				var attrName = computes[i];
				mapHelpers.addComputedAttr(this, attrName, this[attrName]);
			}
		}
function () {
			this._computedAttrs = Object.create(null);

			var computes = this.constructor._computedPropertyNames;

			for (var i = 0, len = computes.length; i < len; i++) {
				var attrName = computes[i];
				mapHelpers.addComputedAttr(this, attrName, this[attrName]);
			}
		}
function ( ) { this . _computedAttrs = Object . create ( null ) ; var computes = this . constructor . _computedPropertyNames ; for ( var i = 0 , len = computes . length ; i < len ; i ++ ) { var attrName = computes [ i ] ; mapHelpers . addComputedAttr ( this , attrName , this [ attrName ] ) ; } }
### _setupComputes Sets up computed properties on a Map. Stores information for each computed property on `this._computedAttrs` that looks like:  ``` { // the number of bindings on this property count: 1, // a handler that forwards events on the compute // to the map instance handler: handler, compute: compute  // the compute } ```
### _setupComputes Sets up computed properties on a Map . Stores information for each computed property on this . _computedAttrs that looks like : { // the number of bindings on this property count : 1 // a handler that forwards events on the compute // to the map instance handler : handler compute : compute // the compute }