Get Names of Array of Objects without Looping-CodePudding

I have an array of country objects (countries) and I'm trying to get just an array of the String names, so from this example:

Just: ['Canada', 'USA', ..] etc.

I'm trying to do this with

const getNames = (countries) => countries.map(({ Name }) => Name);

but I can't seem to get it. Any suggestions?

CodePudding user response：

Just this?

const getNames = countries.map(c => c.Name);

CodePudding user response：

While topic says "without" looping, actually you can't. Map method also creates internal looping algorithm. So basically you can do something very simple and really efficient like standard for loop.

// Array of objects
const arr = [
  { id: 1, Name: "Canada", isSelected: false },
  { id: 2, Name: "USA", isSelected: false },
  { id: 3, Name: "India", isSelected: false }
];

// Function to get all params by name
const getAllParam = (arr, param, res = []) => {
  for(const e of arr) if(e[param]) res.push(e[param]);
  return res;
};

// Get all params with "Name" key
const res = getAllParam(arr, "Name");

// Test
console.log(res);

CodePudding user response：

You're quite close to getting it right; just remove (countries) => and you're good to go.

const getNames = countries.map(({ Name }) => Name);

Alternatively, you can keep your code, which is a function. To get the names of the countries - coNames - call the function and pass countries as a parameter.

const getNames = (countries) => countries.map(({ Name }) => Name); 
const countries = [{id: ...., Name:.........}];
const coNames = getNames( countries );

Your code is equivalent to:

const getNames = function( countries ) {
    return countries.map(function({Name}) {
        return Name;
    });
};