错误处理和调试

//try catch finally
    try {
        Math.floor( 1.3 );
        //window.floor(1.3);
    }
    catch ( error ) {
        W.log( error.message );
    }
    finally {

W.log( 1 ); //无论抛出异常与否finally都会执行 而且如果finally存在是 try catch中的return都将被忽略
    }

//自定义错误
    function CustomError(message){
        this.name="CustomError";
        this.message=message;
    }

CustomError.prototype=new Error();

//    throw  new CustomError("my message");

//控制台调试
    console.error("error");
    console.info("info");
    console.log("log");
    console.warn("warn");