在Javascript中获取数组中每个字符串的第一个字符

Question

let animals = ['Hen', 'elephant', 'llama', 'leopard', 'ostrich', 'Whale', 'octopus', 'rabbit', 'lion', 'dog'];

let secretMessage = animals.map(function(animal) {
     for(animal = 0; animal <= animals.length-1; animal++) {
            return animals[animal].charAt(animal);
     }
});

console.log(secretMessage.join(''));

Hi, thru this piece of code i want to output the string HelloWorld , which is formed by the first characters of each string/element in the animals array. However, the output is instead HHHHHHHHHH . I don't know if the for loop is the problem here?

Could someone please tell me why the code produces such an output and how i can modify it in order for the desired result to be returned successfully?

I'm just a novice for now & that's why your help will play a tremendous part in my growth as a programmer. Thanks in advance!

Answer 1

Map is a for loop in and of itself.

Try:

 // Animals. const animals = ['Hen', 'elephant', 'llama', 'leopard', 'ostrich', 'Whale', 'octopus', 'rabbit', 'lion', 'dog'] // Secret Message. const secretMessage = animals.map((animal) => animal[0]).join('') // Log. console.log(secretMessage) // "HelloWorld"

Or alternatively:

 // Animals. const animals = ['Hen', 'elephant', 'llama', 'leopard', 'ostrich', 'Whale', 'octopus', 'rabbit', 'lion', 'dog'] // Secret Message. const secretMessage = animals.reduce((accumulator, animal) => accumulator + animal[0], '') // Log. console.log(secretMessage) // "HelloWorld"

Answer 2

The map method does the for loop for you. So all you need in the function is animal[0]

let secretMessage = animals.map(function(animal) {
     return animal[0]
});

This will return every first character in every string in the array, animals. Everything else you have is right.

Answer 3

You don't need inner loop:

 let animals = ['Hen', 'elephant', 'llama', 'leopard', 'ostrich', 'Whale', 'octopus', 'rabbit', 'lion', 'dog']; let secretMessage = animals.map(function(animal) { return animal.charAt(0); // or simply animal[0] }); console.log(secretMessage.join(''));

Answer 4

The error here is that you have a loop inside the map function, which already loops the array.

The correct code is

animals.map(x=>x[0]).join('');
//or
animals.map(function(animal){
    return animal[0]; //First letter of word
}).join(''); //Array -> String

Answer 5

This should be the code:

let animals = ['Hen', 'elephant', 'llama', 'leopard', 'ostrich', 'Whale', 'octopus', 'rabbit', 'lion', 'dog'];

let secretMessage = animals.map(function(animal) {
    return animal.charAt(0);
});

console.log(secretMessage.join(''));

Answer 6

Just do this.

 let animals = [ 'Hen', 'elephant', 'llama', 'leopard', 'ostrich', 'Whale', 'octopus', 'rabbit', 'lion', 'dog' ]; console.log(animals.map(e => e[0]).join(""));

Answer 7

let animals = ['Hen', 'elephant', 'llama', 'leopard', 'ostrich', 'Whale', 'octopus', 'rabbit', 'lion', 'dog'];

let secretMessage = animals.map(function(animals) {
return animals[0];
});

console.log(secretMessage.join(''));

or

let animals = ['Hen', 'elephant', 'llama', 'leopard', 'ostrich', 'Whale', 'octopus', 'rabbit', 'lion', 'dog'];

let secretMessage = animals.map(animals => animals[0]);

console.log(secretMessage.join(''));

Answer 8

.map() array function take callback function as an argument and return new array so that can use this method to get our result see the syntax below:

const animals = ['Hen', 'elephant', 'llama', 'leopard', 'ostrich', 'Whale', 'octopus', 'rabbit', 'lion', 'dog'];


 const secretMessage = animals.map(animals => {

   return animals[0];
 })

console.log(secretMessage.join(''));

now when .map method is applied on the animals array its return only the first element of the each string because we use animals[0] which read only first element of each string so our output is HelloWorld

Answer 9

 const animals = ['Hen', 'elephant', 'llama', 'leopard', 'ostrich', 'Whale', 'octopus', 'rabbit', 'lion', 'dog']; const secretMessage = animals.map(animal => { return animal[0]; }) console.log(secretMessage.join(''));

Answer 10

let animals = ['Hen', 'elephant', 'llama', 'leopard', 'ostrich', 'Whale', 'octopus', 'rabbit', 'lion', 'dog'];
animals.map(([animals]) => animals).join('')

Output: HelloWorld