Validating input parameters in JavaScript

Javascript

The list of parameters in a JavaScript function declaration doesn't mean anything ... They are purely for the convenience of accessing these parameters, and there is no limit to how the caller passes the arguments, how the caller wants to pass it, as long as the script is not wrong ...

All, sometimes in order to ensure the robustness of the program, we need to implement the validation of input parameters and the default input parameters. These days the process of learning just write a few simple solutions, put here to do backup.

The first is the legality of the authentication type:

function Validatetype (obj, type) {
if (!) ( obj instanceof type)) {
throw new Error ("Invalid type of the argument of" + Arguments.callee.caller);
}

return true;
}

Then verify that the parameter values are valid:

function Validatevalue (obj, Vfunc) {
Validatetype (Vfunc, Function); Vfunc must be Function object
if (!vfunc (obj)) {
throw new Error ("Invalid value of the argument of" + Arguments.callee.caller);
}
}

Again, the default parameter, if the parameter is undefined (that is, no parameters are passed), then the specified default parameter is used:

function Setdefaultvalue (param, defval) {
var undefined;

if (undefined = = param) {
return defval;
} else {
return param;
}
}

OK, that's all. Can be added later, do what you need to do it ~
They are very simple to use. For example, function add, assuming that the incoming must be a positive number, and B can not pass, the default is 10:

function Add (A, b) {
var adder = Setdefaultvalue (b, 10);

Validatetype (A, number);
Validatetype (adder, number);
Validatevalue (A, function (n) {return n > 0 true:false;});
Validatevalue (adder, function (n) {return n > 0 true:false;});

return a + adder;
}

Well, JavaScript is really fun!