static/ext/src/util/AbstractMixedCollection.js
function(property, value, start, anyMatch, caseSensitive){
        if(Ext.isEmpty(value, false)){
            return -1;
        }
        value = this.createValueMatcher(value, anyMatch, caseSensitive);
        return this.findIndexBy(function(o){
            return o && value.test(o[property]);
        }, null, start);
    }
function(property, value, start, anyMatch, caseSensitive){
        if(Ext.isEmpty(value, false)){
            return -1;
        }
        value = this.createValueMatcher(value, anyMatch, caseSensitive);
        return this.findIndexBy(function(o){
            return o && value.test(o[property]);
        }, null, start);
    }
Finds the index of the first matching object in this collection by a specific property/value.
@param {String} property The name of a property on your objects.
@param {String/RegExp} value A string that the property values
should start with or a RegExp to test against the property.
@param {Number} [start=0] The index to start searching at.
@param {Boolean} [anyMatch=false] True to match any part of the string, not just the beginning.
@param {Boolean} [caseSensitive=false] True for case sensitive comparison.
@return {Number} The matched index or -1
@since Ext 2