What is the best way to retrieve values from a multi-dimensional array?

I am working with Angular and have an array named testUsers that contains sample data as shown below:

this.testUsers = [
    {email: '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="94a5d4f2f5fff1baf7fbf9">[email protected]</a>', name: 'A Smith'},
    {email: '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="93a1d3f5f2f8f6bdf0fcfe">[email protected]</a>', name: 'B Johnson'},
    {email: '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="96a5d6f0f7fdf3b8f5f9fb">[email protected]</a>', name: 'C Dobbs', colours: 
      ['green', 'blue', 'red']
    },
    {email: '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="4d790d2b2c2628632e2220">[email protected]</a>', name: 'D Mew', colours: 
      ['black', 'blue']
    }
]

I want to extract the values from the nested 'colours' array and store them in a new array. However, my current attempt results in an array within an array, but I need individual values instead.

How can I modify this function to achieve the desired result?

this.newArray = this.testUsers.map(value => {
  return value.colours
});
javascriptangulartypescript

Answer №1

One approach is to return a flat array with a default value for any property that is not provided.

const
    testUsers = [{ email: '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="231263454248460d404c4e">[email protected]</a>', name: 'A Smith' }, { email: '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="06344660676d632865696b">[email protected]</a>', name: 'B Johnson' }, { email: '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="a291e2c4c3c9c78cc1cdcf">[email protected]</a>', name: 'C Dobbs', colours: ['green', 'blue', 'red'] }, { email: '<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="55611533343e307b363a38">[email protected]</a>', name: 'D Mew', colours: ['black', 'blue'] }],
    colours = testUsers.flatMap(({ colours = [] }) => colours);

console.log(colours);

Answer №2

let colorsArray = this.testUsers.map((value) => value.colors) // [undefined, undefined, ['green', 'blue', red'], ['black', 'blue']]
let filteredColors = colorsArray.filter((color) => color !== undefined) // [['green', 'blue', red'], ['black', 'blue']]
const finalOutput = filteredColors.flatMap(color => color) // ['green', 'blue', red', 'black', 'blue']

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