Set the default value for the object in javascript

Question

I have a function called addAlert and this function accepts two parameters.

The first parameter of this function is a string and the second parameter of this function is an object. The object has three properties status, position, and align.

I want to set a default value when I did not set any of the properties of this parameter.

addAlert(stringValue,valueObject) {
    //Set the default values for the valueObject
}

Answer 1

You could create a default object with the default properties and use Object.assign() like this:

function addAlert(stringValue, valueObject) {
  const defaultObj = {
    status: "default status",
    position: "default position",
    align: "default align"
  };
  
  valueObject = Object.assign({}, defaultObj, valueObject)
  console.log(valueObject)
}

addAlert('', { status: "status" })
addAlert('', { position: "position", align: "align" })
addAlert('') // valueObject will be undefined

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

You can use Object.assign to create an object with default values:

const defaults = {
  a: 1,
  b: 2,
  c: 3
}

const obj1 = { a: 11 }
const obj2 = { a: 11, c: 33}
const obj3 = { a: 11, b: 22, c: 33 }

const newObj1 = Object.assign({}, defaults, obj1);
const newObj2 = Object.assign({}, defaults, obj2);
const newObj3 = Object.assign({}, defaults, obj3);

console.log(newObj1);
console.log(newObj2);
console.log(newObj3);

Alternatively, you can do the same using spread syntax:

const defaults = {
  a: 1,
  b: 2,
  c: 3
}

const obj1 = { a: 11 }
const obj2 = { a: 11, c: 33}
const obj3 = { a: 11, b: 22, c: 33 }

const newObj1 = { ...defaults, ...obj1};
const newObj2 = { ...defaults, ...obj2};
const newObj3 = { ...defaults, ...obj3};

console.log(newObj1);
console.log(newObj2);
console.log(newObj3);

You can use either of these to set the default values:

addAlert(stringValue,valueObject) {
    const defaults = { status: "INFO", position: "TOP": align: "LEFT" };
    const settings = Object.assign({}, defaults, valueObj);
    /* use settings in the code */
}

or

addAlert(stringValue,valueObject) {
    const defaults = { status: "INFO", position: "TOP": align: "LEFT" };
    const settings = { ...defaults, ...valueObj };
    /* use settings in the code */
}

Answer 3

you can set the parameters default values as follows:

addAlert(stringValue = 'default string',valueObject = {}) {
    //Set the default values for the valueObject
}

For more info please visit Default_parameters

Answer 4

The best way to do that is just to give in the call of the function the default value with it:

addAlert(stringValue = 'default',valueObject = 'default') {
    //Set the default values for the valueObject
}

Now if you want to give a default Value for stringObject.status you have two options: You check if they are undefined and than set give them a default value:

addAlert(stringValue,valueObject) {
    if (valueObject.status == undefined) {
       valueObject.status = 'default';
    }
}

Or you will pass the three diffrent fields all single.

addAlert(stringValue,valueObject.status, etc..) {
    //Set the default values for the valueObject
}

Hope this helps! :)

Answer 5

You can assign the default values in the parameter list it self in the below manner.

    addAlert = (stringValue="defaultString",valueObject={status:"", position:"", align:""})=> {
        console.log(stringValue, valueObject)
    }