I want to check an argument, if it was undefined (or false), I will assign a value to it by deconstructing an object
function test(x){
let obj={x:1,y:2}
if(!x){x}=obj;
}
note: I don't want to use a temporary variable
if(!x){
let {temp}=obj;
x=temp
}
You can not reassign a value to a variable which is passed as an argument to a function. If it is an object, you can, however, add/modify the properties of that object. But reassigning it will make it lose the reference it was holding from the argument. In your case, if something is undefined, you can not update that reference to hold a value.
For example, in your code -
function test(x){
let obj={x:1,y:2}
x = x || obj.x
}
let x = undefined
test(x)
console.log(x) // x is still undefinedWhat you can do is keep an object and update its properties using a function
function test(a){
let obj={x:1,y:2}
a.x = a.x || obj.x
}
let a = {}
test(a)
console.log(a.x) // a.x equals to 1 now
Override x value with in the function and return it like this Code below
function test(x){
let obj={x:1,y:2}
if(!x)x=obj;
if(x.hasOwnProperty('x')){
return x.x;
}
else{
return "object does not have property x";
}
}
console.log(test(undefined)); // {x:1,y:2}
console.log(test(false)); // {x:1,y:2}
console.log(test(true)); // true
x? You should really provide your quesiton with more details.objbe defined in function scope? As it was said, it's unclear what you're trying to achieve.