I have an array of objects with two properties: canais and topicos:

 channel: Array(3)
    0: {canais: 'canal1', topicos: 'topico1'}
    1: {canais: 'canal2', topicos: 'topico2'}
    2: {canais: 'canal3', topicos: 'topico3'}

I want to split into two array of strings called canais and topicos:

canais : [ "canal1" , "canal2", "canal3" ];
topicos: [ "topico1" , "topico2", "topico3" ];

CodePudding user response：

You can do

const canais = channel.map(item => item.canais)
const topicos = channel.map(item => item.topicos)

CodePudding user response：

You could do this in multiple ways:

1. Map each element to a 2-element array [canais, topicos] and then transpose the result to get two arrays (here original is your array):

   const transpose = arr => arr[0].map((x, i) => arr.map(x => x[i]))
   const [canais, topicos] = transpose(original.map(a => [a.canais, a.topicos]))
   

   See also: Transposing a 2D-array in JavaScript which is the origin of the transpose function above.

2. Use a forEach loop and accumulate:

   const canais = []
   const topicos = []
   
   original.forEach(el => {
       canais.push(el.canais)
       topicos.push(el.topicos)
   })
   

3. Normal for loop and accumulate:

   const allCanais = []
   const allTopicos = []
   
   for (const {canais, topicos} of original) {
       allCanais.push(canais)
       allTopicos.push(topicos)
   }
   

4. Map two times (first extract all el.canais then all el.topicos), though this iterates twice over the data which is probably unneeded.

CodePudding user response：

If you need it to be dynamic, you can use a nested for loop to go through each item and create/add to arrays based on the key, then use an object to store each array of values.

let channelNames = {};
for(let c of channel){
    for(let key in c){
        if(!channelNames[key])
            channelNames[key] = [];
        channelNames[key].push(i[key]);
    }
}