extend 对象继承

function extend(o, n, override) {for (var p in n) {if (n.hasOwnProperty(p) && (!o.hasOwnProperty(p) || override))o[p] = n[p];}
}// 默认参数
var options = {pageIndex: 1,pageTotal: 2
};// 新设置参数
var userOptions = {pageIndex: 3,pageSize: 10
}extend(options, userOptions, true);// 合并后
options = {pageIndex: 1,pageIndex: 3,pageSize: 10
}