Question 282250 in Javascript Question posted in
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JavaScript learning – how do I push String elements to String Table and Numbers to Numbers Table

I am learning Java Script because I would like to become Tester.

This is a code that I wrote to sort elements from list which contains numbers and string and push them to another lists.

const table = [1,5,55,23,645,'Arek','Hermiona','Tomek','Irena'];
const tableOfNumbers = [];
const tableOfNames = [];

table.map(elementsPuller => {
    if( typeof(elementsPuller) == String) {
        tableOfNames.push(elementsPuller)
    } else { 
        tableOfNumbers.push(elementsPuller)
    }
})

console.log(`Names elements: ${tableOfNames}`)

console.log(`List elements: ${tableOfNumbers}`)

Output is :
Names elements:
List elements: 1,5,55,23,645,Arek,Hermiona,Tomek,Irena

Should be:
Names elements: Arek,Hermiona,Tomek,Irena
List elements: 1,5,55,23,645,

I spent hour to get it working and nothing.

Tags:

4

Answers


  1. 0

    The typeof operator returns the string.

    The typeof operator returns a string indicating the type of the operand’s value.

    const table = [1, 5, 55, 23, 645, 'Arek', 'Hermiona', 'Tomek', 'Irena'];
const tableOfNumbers = [];
const tableOfNames = [];

table.forEach(elementsPuller => {
  if (typeof elementsPuller === "string") {
    tableOfNames.push(elementsPuller)
  } else {
    tableOfNumbers.push(elementsPuller)
  }
})

console.log(`Names elements: ${tableOfNames}`)

console.log(`List elements: ${tableOfNumbers}`)
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  2. 0

    You could take an object with type as key and push directly.

    Your iteration with map is returning an array, but you do not need this.

    const
    table = [1, 5, 55, 23, 645, 'Arek', 'Hermiona', 'Tomek', 'Irena'],
    tableOfNumbers = [],
    tableOfNames = [],
    types = { string: tableOfNames, number: tableOfNumbers };

for (const elementsPuller of table) 
    types[typeof elementsPuller]?.push(elementsPuller);

console.log(`Names elements: ${tableOfNames}`);
console.log(`List elements: ${tableOfNumbers}`);

    With Object.groupBy and destructuring.

    const
    table = [1, 5, 55, 23, 645, 'Arek', 'Hermiona', 'Tomek', 'Irena'],
    { string: tableOfNames, number: tableOfNumbers } = Object.groupBy(table, v => typeof v);

console.log(`Names elements: ${tableOfNames}`);
console.log(`List elements: ${tableOfNumbers}`);
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  3. 0
    1. The map() method of Array instances creates a new array populated with the results of calling a provided function on every element in the calling array. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map, so it is not the correct method here. What you want is arr.forEach(); https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach
    2. you need to use the strict equals operator ( === );
    3. typeof "a" returns "string" not String;
    4. a nitpick, but elementsPuller is a weird name, ‘item’ or ‘tableItem’ sounds better imo;

    so the correct code would look something like this:

    const table = [1,5,55,23,645,'Arek','Hermiona','Tomek','Irena'];
const tableOfNumbers = [];
const tableOfNames = [];


table.forEach(item => {
    if( typeof item === "string") {
        tableOfNames.push(item)
    } else { 
        tableOfNumbers.push(item)
    }
})

console.log(`Names elements: ${tableOfNames}`)
console.log(`List elements: ${tableOfNumbers}`)
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  4. 0

    Here is a reduce – having an object as accumulator

    const table = [1, 5, 55, 23, 645, 'Arek', 'Hermiona', 'Tomek', 'Irena'],
  types = table
    .reduce((acc, element) => (acc[typeof element].push(element), acc), {string: [],number: []})

console.log(`Strings: ${types.string}`)
console.log(`Numbers: ${types.number}`)

    or reduce where we save ALL types of elements using a Nullish_coalescing_assignment ( the ??=) to create an array per passed type.

    const table = [1, 5, 55, 23, 645, 
'Arek', 'Hermiona', 'Tomek', 'Irena', 
["a","b","c"], () => alert('Hello')
];
const types = table
  .reduce((acc, element) => {
acc[typeof element] ??= []; // nullish coalescing assignment
acc[typeof element].push(element);
return acc ;
  },{});

Object.entries(types)
  .forEach(([key,value]) => console.log(`${key}: ${key === 'object' ? 
    JSON.stringify(value[0]) : value}`)
  );
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