Question

i have some javascript class someClass and have initialization function init which check constructor params. Object with this params are rather huge and this function became too large.

function SomeClass (paramObj) {
    this.inputHourId;
    this.inputHourName;
    this.inputHourValue;
    ......
    ......
    this.Init = function (paramObj) {
        if (typeof paramObj.hourOptions.inputName == "undefined") {
            this.inputHourName = "default_name";
        } else {
            this.inputHourName = paramObj.hourOptions.inputName;
        }

        if (typeof paramObj.hourOptions.inputValue == "undefined") {
            this.inputHourValue = "default_value";
        } else {
            this.inputHourValue = paramObj.hourOptions.inputValue;
        }
        ......
        ......
        ......
    }
    this.Init(paramObj);
}

To avoid code duplication and make it more readable i decide to create function which will do var initialization with check

this.initVar = function (veriable, value) {
    if (typeof value == "undefined") {
        veriable = "some_default_value";
    } else {
        veriable = val;
    }
}

after adding initVar function, my Init function should look like that:

this.Init = function (paramObj) {
    // Input hour initialization
    this.initVar(this.inputHourId, paramObj.hourOptions.inputId);
    this.initVar(this.inputHourName, 
paramObj.hourOptions.inputName);
    this.initVar(this.inputHourValue, paramObj.hourOptions.inputValue);
    ....
    ....
    ....
}

but after that class vars this.inputHourName are still undefined

Now the question. How can I init my class property with the help of function? Or how can i transmit class property like function parametr?

Answer 1

That’s because when you pass this.inputHourId to initVar() it will make a copy of the variable when it’s being updated; that’s not what you want.

You can rewrite initVar() to this; it uses the name of the variable as a string rather than the variable itself. Then it uses this[variable] to update the actual instance variable.

this.initVar = function (variable, value) {
    if (typeof value == "undefined") {
        this[variable] = "some_default_value";
    } else {
        this[variable] = val;
    }
}

Then, you call it like:

this.initVar('inputHourId', paramObj.hourOptions.inputId);