function create_variable(num){
    var name = "test_"+num;   //生成函数名
    window[name] = 100;
    window['name'] = 200;   //注意看中括号里的内容加引号和不加引号的区别
}
 
create_variable(2);
alert(test_2);  // 100;
alert(name); //200;