I have a javascript function that takes an object as a parameter like this:
const someFunc = ({ a }) => { <do something> }
I call the function like this:
a = 'some value'
someFunc({ a })
But sometimes, I need to call the function without passing a. In that case, I need to use a default value for a. How can I add a default value for a key inside an object?
I think you're looking for default parameters
const someFunc = ({ a = "foo" }) => {
console.log(a);
}
someFunc({}); // "foo"
someFunc({a: "bar"}); // "bar"Update
If you also want to have a as default to "foo" without passing any argument, you need to set a default parameter also for the object that contains a. Something like:
const someFunc = ({ a = "foo" } = {}) => {
console.log(a);
}
someFunc(); // "foo"
Uncaught TypeError: Cannot read property 'a' of undefined
someFunc() call. If the OP want to call someFunc also without passing anything, the function signature should include that.Your edit should have added any object to the someFunc() call No, that's precisely the point, OP wants a default parameter if none is passed, so...a is the property, not the object. And that I replied to. If he meant the whole object, I edited my answer to cover that scenario too. But it's not what he wrote.const someFunc = ({a, b, c ,d} = {a:10, b: 12, c:3, d:4}) => {
console.log(a, b, c ,d);
}
someFunc()Remember that this code wont actually work in IE.
Here is the workaround for IE:
var someFunc = function someFunc() {
var _ref = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {
a: 10
},
a = _ref.a;
//here starts the function
console.log(a);
};
someFunc();
someFunc({})? This might be required if I have multiple keys inside the object.someFunc({}). Here I am passing an empty object instead of nothing.ES6 accepts default values for parameters :
const someFunc = ({a} = {a : 6}) => {
console.log({a})
}
someFunc({ a : 3 })
someFunc()someFunc({})? This might be required if I have multiple keys inside the object.someFunc = (obj = {a : 6}). If the answer worked for you, please don't forget to mark it as accepted!const someFunc = ({ a }) => {
typeof a === 'undefined'
? a = 'some default'
: a = a;
console.log(a);
}
a = 'some value';
someFunc({ a });
someFunc({});
a = a === undefined ? "default" : a rather than (ab)use assignment expressions. Could you provide an explanation for why this is preferable to the existing answers?