如何使用 Object.entries() 方法 JavaScript 从 1 开始迭代？

Question

const game = {
  team1: 'Bayern Munich',
  team2: 'Borrussia Dortmund',
  players: [
    [
      'Neuer',
      'Pavard',
      'Martinez',
      'Alaba',
      'Davies',
      'Kimmich',
      'Goretzka',
      'Coman',
      'Muller',
      'Gnarby',
      'Lewandowski',
    ],
    [
      'Burki',
      'Schulz',
      'Hummels',
      'Akanji',
      'Hakimi',
      'Weigl',
      'Witsel',
      'Hazard',
      'Brandt',
      'Sancho',
      'Gotze',
    ],
  ],
  score: '4:0',
  scored: ['Lewandowski', 'Gnarby', 'Lewandowski', 'Hummels'],
  date: 'Nov 9th, 2037',
  odds: {
    team1: 1.33,
    x: 3.25,
    team2: 6.5,
  },
};

1) Loop over the game.scored array and print each player name to the console,along with the goal number start from 1 like (Goal 1: etc)

This is my first solution and the result is perfect:

for (const [i, v] of game.scored.entries()) 
{
  console.log(`Goal: ${i + 1} ${v}`);
}

Output:

Goal: 1 Lewandowski

Goal: 2 Gnarby

Goal: 3 Lewandowski

Goal: 4 Hummels

Picture Result:

The issue is when I tried from different method using Object.entries() the itration don't start from 1

Soultion 2

for (const [i, v] of Object.entries(game.scored)) 
{
  console.log(`Goal: ${i+1} ${v}`);
}

Output:

Goal: 01 Lewandowski

Goal: 11 Gnarby

Goal: 21 Lewandowski

Goal: 31 Hummels

Picture Result:

Answer 1

The first approach takes the array and its entries ( Array#entries ), whereas the second one takes the object and the entries from the object ( Object.entries ).

Objects has only strings or symbols as keys. To take a number as value you need to convert it to a number. The shortest way is to take an unary plus + .

 const game = { team1: 'Bayern Munich', team2: 'Borrussia Dortmund', players: [['Neuer', 'Pavard', 'Martinez', 'Alaba', 'Davies', 'Kimmich', 'Goretzka', 'Coman', 'Muller', 'Gnarby', 'Lewandowski'], ['Burki', 'Schulz', 'Hummels', 'Akanji', 'Hakimi', 'Weigl', 'Witsel', 'Hazard', 'Brandt', 'Sancho', 'Gotze']], score: '4:0', scored: ['Lewandowski', 'Gnarby', 'Lewandowski', 'Hummels'], date: 'Nov 9th, 2037', odds: { team1: 1.33, x: 3.25, team2: 6.5 } }; for (const [i, v] of Object.entries(game.scored)) { console.log(`Goal: ${+i + 1} ${v}`); }

Answer 2

game.scored.entries() returns an iterator object in which the indexes are returned as numbers. So adding 1 to the value of i performs the addition and gives you the expected result.

Object.entries(game.scored) returns the key as a string. So when you do i + 1 in the second code example, instead of doing an addition, your code performs concatenation. Since i is a string, 1 will be converted to string and then concatenated with the value of i .

To get the desired result, convert i to a number before adding 1 to it.

There are multiple ways to convert a string to a number. You can use one of the following ways:

• Using + unary operator

  for (const [i, v] of Object.entries(game.scored)) { console.log(`Goal: ${(+i)+1} ${v}`); }

• Using parseInt() function

   for (const [i, v] of Object.entries(game.scored)) { console.log(`Goal: ${parseInt(i) + 1} ${v}`); }

• Using Number() constructor

   for (const [i, v] of Object.entries(game.scored)) { console.log(`Goal: ${Number(i) + 1} ${v}`); }