let obj2 = {
level2:{
data:"data"
}
}
let obj2Array = [obj2,obj2,obj2];
obj2Array.map(obj=>{
obj = obj.levle2.data
});
console.log(obj2Array)
what I'm expecting is ["data","data","data"].But I still got the original data. I know I can use forEach() to achieve this, but why I can't reassignment element in map()?
Because .map() does not mutate the original array, it returns a new one, so you should do sth like this:
let obj2Array = [obj2,obj2,obj2];
obj2Array = obj2Array.map(obj=>{
obj = obj.levle2.data
});
console.log(obj2Array)
You forgot to set obj2Array to the value returned by .map(). See below:
var obj2 = {
level2:{
data:"data"
}
}
var obj2Array = [obj2,obj2,obj2];
// set to returned map
obj2Array = obj2Array.map(obj=>{
return obj2.level2.data
});
console.log(obj2Array)Map will return new array
const result = obj2Array.map(obj=>{
return obj2.levle2.data
});
console.log(result)
map() returns a new array. Try this code:
let obj2 = {
level2:{
data:"data"
}
}
let obj2Array = [obj2,obj2,obj2];
obj2Array = obj2Array.map(obj=>
obj.level2.data
);
console.log( obj2Array )
output ["data", "data", "data"]
the map() method creates a new array populated with the results of calling a provided function on every element in the calling array. as this says in the documentation you can reAssign the obj2Array when doing map
like this
let obj2 = {
level2:{
data:"data"
}
}
let obj2Array = [obj2,obj2,obj2];
obj2Array = obj2Array.map(obj=>{
return obj.level2.data
});
console.log( obj2Array )
// now it is ["data","data","data"];
obj.level2.datanotobj2.levle2.data