Multiple typescript constructors

Question

I’m struggling with TS constructors. Ill post this on stackoverflow, also.

Say you want to make the equivalent of these three constructors:

public Animal(){
    this.name = “default”;
    this.noise =””;
public Animal(string name){
    this.name = name;
    this.noise = “”;
}
public Animal(string name, string noise){
    this.name = name;
    this.noise = noise;
}

Do you do something like this in Typescript?

Constructor(name?:string, noise?:string){
    if(name!= null)
        this.name =name;
    else


     this.name = "";
        if(string != null)
            this.noise = noise;
        else
            this.noise = "";
}

And so forth?

What about if you also have various primitives coming in say, you could declare an animal with an int or a string. Do you just use instanceof?

Thanks! Nathan

Ryan Cavanaugh · Accepted Answer · 2014-05-19 18:43:45Z

3

This can be done very simply:

class Animal {
    public name: string;
    public noise: string;

    constructor(name = 'default', noise = '') {
        this.name = name;
        this.noise = noise;
    }
}

This is also exactly equivalent to:

class Animal {
    constructor(public name = 'default', public noise = '') {
    }
}

Note that missing parameters in JavaScript have the value undefined, not null.

edited May 19, 2014 at 18:43

answered May 19, 2014 at 18:31

Ryan Cavanaugh

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