I am a totally new to coding and I'm practicing loops and arrays. I created an array with multiple sub arrays that contain pairs of strings. I'm trying to pull out and isolate each string using a nested for loops.
Here is my code:
const pairs = [['Blue', 'Green'],['Red', 'Orange'],['Pink', 'Purple']];
//attempting to use nested arrays to get each string from an array
function getString(arr){
//this loop should grab each array in the list of arrays
for (let i = 0; i < arr.length; i++){
console.log(i , arr[i]);
//this should assign each sub array to a new var to be iterated over
subArr = arr[i];
} for (let j = 0; j < subArr.length; j++){
console.log(j, arr[j]);
}
};
console.log(getString(pairs));
the problem is the output is of the last for loop is : ['Pink', 'Purple'] not each color extracted from the nested loops.
What am I doing wrong here?
Mirii
You should nest the for loops like this:
for (let i = 0; i < arr.length; i++) {
console.log(i, arr[i]);
//this should assign each sub array to a new var to be iterated over
subArr = arr[i];
for (let j = 0; j < subArr.length; j++) {
console.log(j, arr[j]);
}
}
How you have it, they'd run one after the other.
The solution is provided
:
function getString(arr) {
let arrResult = [];
for (let i = 0; i < arr.length; i++) {
for (let j = 0; j < arr[i].length; j++) {
arrResult.push(arr[i][j]);
}
}
return arrResult;
}
You need to nest the loops, just like you are nesting the arrays. Also, unless you want to alter i or j, I suggest you use .forEach as it is more simple to work with.
Example:
pairs.forEach((pair, i) => {
pair.forEach((subPair, j) => {
console.log(j, subPair);
});
});
You may also make a variable, push to it within the pair.forEach function, and return it at the end of your root function.
I hope this answers your question, thank you for posting, and have a nice day. ;P
Your loops aren't actually nested: you close the first loop before starting the second one. Because subArr is a global varialbe (no let, const, or var keyword), it's still defined in the second loop, but that's not an ideal way to do things. You also need to log arr[i][j] rather than what you have.
This fixes those issues:
function getString(arr) {
//this loop should grab each array in the list of arrays
for (let i = 0; i < arr.length; i++){
//this should assign each sub array to a new var to be iterated over
let subArr = arr[i];
for (let j = 0; j < subArr.length; j++){
console.log(arr[i][j]);
}
}
};
getString(pairs);
Another issue you have is that you're calling console.log(getString(pairs)), but getString doesn't return anything, it's logging itself. If you want it to return, for example, a newline-delimited string of all the items, you could push items to an array and return them joined with a newline (or whatever character you want):
function getString(arr) {
let ret = []
//this loop should grab each array in the list of arrays
for (let i = 0; i < arr.length; i++){
//this should assign each sub array to a new var to be iterated over
let subArr = arr[i];
for (let j = 0; j < subArr.length; j++){
ret.push(arr[i][j]);
}
}
return ret.join('\n')
};
console.log(getString(pairs));
Nested loops themselves aren't ideal, since they're not as readable as using array methods. Using forEach takes much less code:
function getString (arr) {
arr.forEach(function (subArr) {
console.log(subArr[0])
console.log(subArr[1])
})
}
getString(pairs)
Or, more succinctly, you can use map:
function getString (arr) {
return arr.map(([ a, b ]) => `${a}\n${b}`).join('\n');
}
console.log(getString(pairs))
Even more succinctly, you can do this with [].flat():
const getString = (xs = []) => xs.flat().join('\n')
console.log(getString(pairs))
Related
I tried to get this to work, but the outer loop stops after second iteration, and everything that's after it does not execute(just like it was the end of the script). I want to fill two dimensional array with any character(here i used 'q' as an example)
var A=[[],[]];
for(var i=0;i<12;i++){
for(var j=0;j<81;j++){
A[i][j]='q';
}
}
It didn't work, so i put alert(i+' '+j); to see if it's even executing, and, as i wrote before, it stops after second iteration of outer loop, and then ignores rest of the script.
All I want is to have this array filled with same character in the given range(12 rows, 81 columns in this specific case), so if there's no hope in this method, i'll be glad to see one that works.
This does the job in one line.
var A = Array(12).fill(null).map(()=>Array(81).fill('q'))
This is an array of references and a bad idea as harunurhan commented.
var A = Array(12).fill(Array(81).fill('q'));
The Array.from() method creates a new, shallow-copied Array instance
from an array-like or iterable object.
function createAndFillTwoDArray({
rows,
columns,
defaultValue
}){
return Array.from({ length:rows }, () => (
Array.from({ length:columns }, ()=> defaultValue)
))
}
console.log(createAndFillTwoDArray({rows:3, columns:9, defaultValue: 'q'}))
var A=[[], []];
^ This line declares a two dimensional array of size 1x2. Try this instead:
var A = [];
for (var i = 0; i < 12; i++) {
A[i] = [];
for (var j = 0; j < 81; j++) {
A[i][j] = 'q';
}
}
Since fill() is the most succinct and intuitive, and it works as intended for immutable values, my preference would be an outer from() and an inner fill():
Array.from({length: 12}, _ => new Array(81).fill('q'));
The best approach to fill up 2D array would be like the following
let array2D = [], row = 3, col = 3, fillValue = 1
for (let i = 0; i < row; i++){
let temp = []
for (let j = 0; j < col; j++){
temp[j] = fillValue
}
array2D.push(temp)
}
You need to initialise a new array for i each time the first loop runs, and you don't need to set the layout of the array before you create it (Remove the [], [] inside the declaration of A). Try this:
var A = [];
for (var i = 0; i < 12; i++) {
A[i] = [];
for (var j = 0; j < 81; j++) {
A[i][j] = 'q';
}
}
console.log(A);
.as-console-wrapper {
max-height: 100% !important;
top: 0;
}
I have an array (tot) with arrays in it.
I need to check each entry in (tot) for a value , which is done at console by typing AA[3] , however, when I execute it from a script, AA[3] would NOT return any value!
here is my script:
tot=["AA","AB","AC"];
AA=["1","2","3","4","5","6","7"];
AB=["1","2","3","4","5","6","7"];
AC=["1","2","3","4","5","6","7"];
for (let i = 0; i < tot.length; i++)
{
tot[i]+'[2]';
}
I have an array (tot) with arrays in it
Actually that's inaccurate. You have an array with string values inside that are not arrays. The values of the strings you have in your array match the names of some arrays. Instead of this you might want to use an object of arrays, like:
let AA=["1","2","3","4","5","6","7"];
let AB=["1","2","3","4","5","6","7"];
let AC=["1","2","3","4","5","6","7"];
let tot={AA,AB,AC};
let index = 5;
for (let key in tot) {
console.log(`${key}[${index}]: ${tot[key][index]}`);
}
You could try:
const tot = [
["1","2","3","4","5","6","7"],
["1","2","3","4","5","6","7"],
["1","2","3","4","5","6","7"]
];
for (let i = 0; i < tot.length; i++)
{
console.log(tot[i][2]);
}
Variables do not work as functions. Instead of writing variables in a loop, try:
console.log(tot);
Also, I assume you meant to do var tot = new Array(AA, AB, AC);
var AA=["1","2","3","4","5","6","7"];
var AB=["1","2","3","4","5","6","7"];
var AC=["1","2","3","4","5","6","7"];
var tot= new Array(AA,AB,AC);
for (let i = 0; i < tot.length; i++)
{
tot[i].push("2")
console.log(tot[i]);
}
To loop through every array inside tot array, you have to nest two for loops, and console.log each value in nested for loop:
const AA=["1","2","3","4","5","6","7"];
const AB=["1","2","3","4","5","6","7"];
const AC=["1","2","3","4","5","6","7"];
const tot=[AA,AB,AC];
const logArray = (tot) => {
for (let i = 0; i < tot.length; i++) {
console.warn(`tot[${i}] contains:`);
for (let j = 0; j < tot[i].length; j++) {
console.log(tot[i][j]);
}
}
};
Your code doesn't output anything, because you didn't ask it to. also that line: tot[i] + '[2]' is not correct. What exactly are you trying to do there. I changed it to add '[2]' string to each element, but doesn't seem that that is what you want.
tot=["AA","AB","AC"];
AA=["1","2","3","4","5","6","7"];
AB=["1","2","3","4","5","6","7"];
AC=["1","2","3","4","5","6","7"];
for (let i = 0; i < tot.length; i++)
{
tot[i]+='[2]';
}
console.log(tot)
Why I am getting this kinda error. But when I am calculating products of them, they seem fine.
//The funtion will add all the values in that array....
function addArrayValues(arr) {
var addition = 0;
for (var i = 0; i < arr.length; i++) {
for (var j = 0; j < arr[i].length; j++) {
addition += arr[i][j];
}
}
return addition;
}
var addition = addArrayValues([[[23], [34], [54]], [[34], [75]], [[75]], [65]]);
console.log(addition);
You don't have an array of arrays - rather, you have an array of arrays of arrays. You need to go 3 levels deep, not just 2:
//The funtion will add all the values in that array....
function addArrayValues(arr){
var addition=0;
for(var i=0;i<arr.length;i++){
for(var j=0;j<arr[i].length;j++){
for (var k = 0; k < arr[i][j].length; k++) {
addition+=arr[i][j][k];
}
}
}
return addition;
}
var addition=addArrayValues([[[23],[34],[54]],[[34],[75]],[[75]],[65]]);
console.log(addition);
Or use .flat instead:
//The funtion will add all the values in that array....
const addArrayValues = arr => arr
.flat(2)
.reduce((a, b) => a + b, 0);
var addition=addArrayValues([[[23],[34],[54]],[[34],[75]],[[75]],[65]]);
console.log(addition);
Your original code is implicitly coercing the 3-deep arrays to strings first, so, eg, iterating over
[[23],[34],[54]]
starts by calculating
[23] + [34] + [54]
so the arrays are turned to strings during the creation of the addition variable.
I tried to get this to work, but the outer loop stops after second iteration, and everything that's after it does not execute(just like it was the end of the script). I want to fill two dimensional array with any character(here i used 'q' as an example)
var A=[[],[]];
for(var i=0;i<12;i++){
for(var j=0;j<81;j++){
A[i][j]='q';
}
}
It didn't work, so i put alert(i+' '+j); to see if it's even executing, and, as i wrote before, it stops after second iteration of outer loop, and then ignores rest of the script.
All I want is to have this array filled with same character in the given range(12 rows, 81 columns in this specific case), so if there's no hope in this method, i'll be glad to see one that works.
This does the job in one line.
var A = Array(12).fill(null).map(()=>Array(81).fill('q'))
This is an array of references and a bad idea as harunurhan commented.
var A = Array(12).fill(Array(81).fill('q'));
The Array.from() method creates a new, shallow-copied Array instance
from an array-like or iterable object.
function createAndFillTwoDArray({
rows,
columns,
defaultValue
}){
return Array.from({ length:rows }, () => (
Array.from({ length:columns }, ()=> defaultValue)
))
}
console.log(createAndFillTwoDArray({rows:3, columns:9, defaultValue: 'q'}))
var A=[[], []];
^ This line declares a two dimensional array of size 1x2. Try this instead:
var A = [];
for (var i = 0; i < 12; i++) {
A[i] = [];
for (var j = 0; j < 81; j++) {
A[i][j] = 'q';
}
}
Since fill() is the most succinct and intuitive, and it works as intended for immutable values, my preference would be an outer from() and an inner fill():
Array.from({length: 12}, _ => new Array(81).fill('q'));
The best approach to fill up 2D array would be like the following
let array2D = [], row = 3, col = 3, fillValue = 1
for (let i = 0; i < row; i++){
let temp = []
for (let j = 0; j < col; j++){
temp[j] = fillValue
}
array2D.push(temp)
}
You need to initialise a new array for i each time the first loop runs, and you don't need to set the layout of the array before you create it (Remove the [], [] inside the declaration of A). Try this:
var A = [];
for (var i = 0; i < 12; i++) {
A[i] = [];
for (var j = 0; j < 81; j++) {
A[i][j] = 'q';
}
}
console.log(A);
.as-console-wrapper {
max-height: 100% !important;
top: 0;
}
I have an array like var arr = { 30,80,20,100 };
And now i want to iterate the above array and add the iterated individual values to one function return statement for example
function iterate()
{
return "Hours" + arr[i];
}
I had tried in the following approach
function m()
{
for(var i in arr)
{
s = arr[i];
}
document.write(s);
}
The above code will gives only one value i.e. last value in an array. But i want to iterate all values like
30---for first Iteration
80---for second Iteraton
Any help will be appreciated
Iterate over using the length property rather than a for ... in statement and write the array value from inside the loop.
for (var ii = 0, len = arr.length; ii < len; ii++) {
document.write(arr[ii]);
}
That's because your write statement is outside the loop. Don't you want it like this?
function m(arr) {
for (var i = 0; i < arr.length; i++) {
s = arr[i];
document.write(s);
}
}
Also, don't use in because it will give you ALL the properties of array. Use array.length