Function reduce

libs/echarts/echarts.simple.js:585–598

* @memberOf module:zrender/core/util * @param {Array} obj * @param {Function} cb * @param {Object} [memo] * @param {*} [context] * @return {Array}

(obj, cb, memo, context)

 * @return {Array}
 */
function reduce(obj, cb, memo, context) {
    if (!(obj && cb)) {
        return;
    }
    if (obj.reduce && obj.reduce === nativeReduce) {
        return obj.reduce(cb, memo, context);
    }
    else {
        for (var i = 0, len = obj.length; i < len; i++) {
            memo = cb.call(context, memo, obj[i], i, obj);
        }
        return memo;
    }
}

/**
 * 数组过滤