Find nested array by value

Question

I've searched high and low for an answer to this, but nothing.

I have a nested array and want to find it by exact value but can't seem to get it to work:

let rowLetters = ["A","B","C",["D","E"],"F"];
for(n=0;n<rowLetters.length;n++){
 if(rowLetters[n] === ["D","E"]){
 console.log("Found");
 }
 console.log(rowLetters[n]);
}
Console Output:
"A"
"B"
"C"
["D","E"] // <-- There it is..
"F"

What am I doing wrong?

• Sysix: don't strict type check it
• user12407908: Can the nesting go deeper than what you show?
• user12407908: BTW, don't use JSON.stringify for this as too many answers show. That's not a sensible means of simple value comparison.

Answer 1

You need to check

• if item is an array,
• if item has the same length as the wanted value array and
• if the values of the arrays are equal.

let rowLetters = ["A", "B", "C", ["D", "E"], "F"],
 search = ["D", "E"];
for (const item of rowLetters) {
 if (Array.isArray(item) && item.length === search.length && search.every((v, i) => item[i] === v)) {
 console.log(item);
 }
}

Answer 2

You can use filter with JSON.stringify()

let data = ["A", "B", "C", ["D", "E"], "F"];
let search = data.filter(ele => JSON.stringify(ele) == JSON.stringify(["D", "E"]));
if (search.length > 0) {
 console.log("found")
}

Answer 3

Are you looking for something like find() mixed with Array.isArray()?

let rowLetters = ["A","B","C",["D","E"],"F"];
console.log(rowLetters.find(i => Array.isArray(i)))

You cannot compare an array to an array because you are comparing by a reference and not a value. You can however cast the value to a json string and compare, however, this requires exact order in both arrays.

let rowLetters = ["A","B","C",["D","E"],"F"];
for(let i of rowLetters){
 if(JSON.stringify(i) === JSON.stringify(["D","E"])) {
 console.log("Found");
 }
}

• gatzkerob: Possibly, I want to find it by exact value: the array ["D","E"]

Answer 4

You can use .find and JSON.stringify:

let rowLetters = ["A","B","C",["D","E"],"F"];
let arrayToFind = JSON.stringify(["D","E"])
let nestedArray = rowLetters.find( arr => JSON.stringify(arr) === arrayToFind );
 
console.log(nestedArray);

A better way to check if two arrays are equal would be using .every and .includes as follows:

let rowLetters = ["A","B","C",["D","E"],"F"];
const arraysAreEqual = (arr1, arr2) => {
 if(arr1.length != arr2.length) return false;
 return arr1.every( e => arr2.includes(e) );
}
const arrayToFind = ["D","E"];
let nestedArray = rowLetters.find( arr => arraysAreEqual(arr, arrayToFind) );
 
console.log(nestedArray);

• user12407908: Serializing every single value for mere value comparison just seems wrong. Serializing the unchanged target array over and over is even worse.