Develop Reference

javascript iterate through and map a multi-dimensional array

I want to apply a function to each of the values at all levels of the array:
arr = [[1,2,3],[1,2,3],[[1,2],[1,2]],1,2,3]
for example, multiply all the values by 3, and map it in the same format as before so I get:
arr = [[3,6,9],[3,6,9],[[3,6],[3,6]],3,6,9]
What would be the best way to go about this?
I tried to use a recursive function:
function mapall(array){
array.map(function(obj){
if (Array.isArray(obj)===true) { return mapall(obj) }
else{ return obj*3 }
})
};
but when I run it I just get undefined, so I must be doing something not quite right??
Any ideas??
Thanks

Everything was working, but you forgot to return from array.map. Here's a cleaner version of your code:
var arr = [[1,2,3],[1,2,3],[[1,2],[1,2]],1,2,3];
function mapAll(array){
return array.map(function(item){
return Array.isArray(item) ? mapAll(item) : item * 3;
});
}
alert(JSON.stringify(mapAll(arr)));

Version with callback function where you can do with array elements what you want (el * 2 or something else)
var arr = [[1,2,3],[1,2,3],[[1,2],[1,2]],1,2,3];
function mapAll(array, cb) {
for (var i = 0, len = array.length; i < len; i++) {
if (Array.isArray(array[i])) {
mapAll(array[i], cb);
} else {
array[i] = cb(array[i]);
}
}
return array;
};
var res = mapAll(arr, function (el) {
return el * 3;
});
console.log(JSON.stringify(res));

Array.prototype.indexOf() cannot find array inside of multi-dimensional array [duplicate]

Let's say we have the following js array
var ar = [
[2,6,89,45],
[3,566,23,79],
[434,677,9,23]
];
var val = [3,566,23,79];
Is there a js builtin function or jQuery one with which you can search the array ar for val?
Thanks
***UPDATE*************
Taking fusion's response I created this prototype
Array.prototype.containsArray = function(val) {
var hash = {};
for(var i=0; i<this.length; i++) {
hash[this[i]] = i;
}
return hash.hasOwnProperty(val);
}

you could create a hash.
var ar = [
[2,6,89,45],
[3,566,23,79],
[434,677,9,23]
];
var hash = {};
for(var i = 0 ; i < ar.length; i += 1) {
hash[ar[i]] = i;
}
var val = [434,677,9,23];
if(hash.hasOwnProperty(val)) {
document.write(hash[val]);
}

You can also use a trick with JSON serializing. It is short and simple, but kind of hacky.
It works, because "[0,1]" === "[0,1]".
Here is the working demo snippet:
Array.prototype.indexOfForArrays = function(search)
{
var searchJson = JSON.stringify(search); // "[3,566,23,79]"
var arrJson = this.map(JSON.stringify); // ["[2,6,89,45]", "[3,566,23,79]", "[434,677,9,23]"]
return arrJson.indexOf(searchJson);
};
var arr = [
[2,6,89,45],
[3,566,23,79],
[434,677,9,23]
];
document.body.innerText = arr.indexOfForArrays([3,566,23,79]);

function indexOfArray(val, array) {
var hash = {};
for (var i = 0; i < array.length; i++) {
hash[array[i]] = i;
}
return (hash.hasOwnProperty(val)) ? hash[val] : -1;
};
I consider this more useful for than containsArray(). It solves the same problem (using a hash table) but returns the index (rather than only boolean true/false).

Can you try this?
var ar = [
[2,6,89,45],
[3,566,23,79],
[434,677,9,23]
];
var val = [3,566,23,79];
var sval = val.join("");
for(var i in ar)
{
var sar = ar[i].join("");
if (sar==sval)
{
alert("found!");
break;
}
}

Why don't you use javascript array functions?
function filterArrayByValues(array, values) {
return array.filter(function (arrayItem) {
return values.some(function (value) {
return value === arrayItem;
});
});
}
Or if your array is more complicated, and you want compare only one property but as result return whole object:
function filterArrayByValues(array, values, propertyName) {
return array.filter(function (arrayItem) {
return values.some(function (value) {
return value === arrayItem[propertyName];
});
});
}
More about used functions: filter() and some()

You can use Array.prototype.some(), Array.prototype.every() to check each element of each array.
var ar = [
[2, 6, 89, 45],
[3, 566, 23, 79],
[434, 677, 9, 23]
];
var val = [3, 566, 23, 79];
var bool = ar.some(function(arr) {
return arr.every(function(prop, index) {
return val[index] === prop
})
});
console.log(bool);

I guess there is no such JS functionality available. but you can create one
function arrEquals( one, two )
{
if( one.length != two.length )
{
return false;
}
for( i = 0; i < one.length; i++ )
{
if( one[i] != two[i] )
{
return false;
}
}
return true;
}

The problem with this is that of object/array equality in Javascript. Essentially, the problem is that two arrays are not equal, even if they have the same values. You need to loop through the array and compare the members to your search key (val), but you'll need a way of accurately comparing arrays.
The easiest way round this is to use a library that allows array/object comparison. underscore.js has a very attractive method to do this:
for (var i = 0; i < ar.length; i++) {
if (_.isEqual(ar[i], val)) {
// value is present
}
}
If you don't want to use another library (though I would urge you to -- or at least borrow the message from the Underscore source), you could do this with JSON.stringify...
var valJSON = JSON.stringify(val);
for (var i = 0; i < ar.length; i++) {
if (valJSON === JSON.stringify(ar[i]) {
// value is present
}
}
This will almost certainly be significantly slower, however.

You can use toString convertion to compare elements
var ar = [
[2,6,89,45],
[3,566,23,79],
[434,677,9,23]
];
var val = [3,566,23,79];
s = !ar.every(a => (a.toString() != val.toString()));
console.log(s) // true

Use this instead
if (ar.join(".").indexOf(val) > -1) {
return true;
} else {
return false;
}

Use lodash isEqual
const isValIncludedInAr = ar.some(element => isEqual(element, val))

const arrayOne = [2,6,89,45];
const arrayTwo = [3,566,23,79];
const arrayThree = [434,677,9,23];
const data = new Set([arrayOne, arrayTwo, arrayThree]);
// Check array if exist
console.log( data.has(arrayTwo) ); // It will return true.
// If you want to make a set into array it's simple
const arrayData = [...data];
console.log(arrayData); // It will return [[2,6,89,45], [3,566,23,79], [434,677,9,23]]

Finding my object inside JSON by its ID

[
{"ID":"5","Name":"Jay"},
{"ID":"30","Name":"Sharon"},
{"ID":"32","Name":"Paul"}
]
So I have this kind of JSON.
I need to easily supply the value for a required key.
For example:
30 would yield => "Sharon"
5 would yield => "Jay"
etc. What is the right way to do this?

Iterate the array and check if the ID matches
function getById(id) {
var O = null;
for (var i=0; i<arr.length; i++) {
if ( arr[i].ID == id ) return O = arr[i];
}
return O;
}
getById('30'); // returns {"ID":"30","Name":"Sharon"}
FIDDLE
or in newer browsers:
function getById(arr, id) {
return arr.filter(function(o) { return o.ID == id });
}
FIDDLE

Try a linear search:
var searchId = "30";
for(var i = 0; i < json.length; i++)
{
if(json[i].ID == searchId)
{
// Found it.
//
break;
}
}

If the IDs will be unique, and if you're going to need to do this frequently, then you may want to convert your collection to key/value pairs where the ID is the key.
var byId = data.reduce(function(res, obj) {
res[obj.ID] = obj;
return res
}, {});
Now you can simply use the ID to look up the object.
var target = byId["30"];

You could probably just write something to loop through it.
var data = [ {"ID":"5","Name":"Jay"},{"ID":"30","Name":"Sharon"}, {"ID":"32","Name":"Paul"} ];
for(var i in data){
if(data[i]["ID"] == 30){
return data[i]["Name"];
}
}

undersocre.js can find a object in collection by one line code
Reference: http://underscorejs.org/#find
Code:
var people = [
{"ID":"5","Name":"Jay"},
{"ID":"30","Name":"Sharon"},
{"ID":"32","Name":"Paul"}
];
_.find(people, function(person) { return person.ID === '5'; });
FIDDLE

The best way to remove array element by value

I have an array like this
arr = ["orange","red","black","white"]
I want to augment the array object defining a deleteElem() method which acts like this:
arr2 = arr.deleteElem("red"); // ["orange","black","white"] (with no hole)
What is the best way to accomplish this task using just the value parameter (no index)?

Here's how it's done:
var arr = ["orange","red","black","white"];
var index = arr.indexOf("red");
if (index >= 0) {
arr.splice( index, 1 );
}
This code will remove 1 occurency of "red" in your Array.

Back when I was new to coding I could hardly tell what splice was doing, and even today it feels less readable.
But readability counts.
I would rather use the filter method like so:
arr = ["orange","red","black","white","red"]
arr = arr.filter(val => val !== "red");
console.log(arr) // ["orange","black","white"]
Note how all occurrences of "red" are removed from the array.
From there, you can easily work with more complex data such as array of objects.
arr = arr.filter(obj => obj.prop !== "red");

There is an underscore method for this, http://underscorejs.org/#without
arr = ["orange","red","black","white"];
arr = _.without(arr, "red");

The trick is to go through the array from end to beginning, so you don't mess up the indices while removing elements.
var deleteMe = function( arr, me ){
var i = arr.length;
while( i-- ) if(arr[i] === me ) arr.splice(i,1);
}
var arr = ["orange","red","black", "orange", "white" , "orange" ];
deleteMe( arr , "orange");
arr is now ["red", "black", "white"]

Array.prototype.deleteElem = function(val) {
var index = this.indexOf(val);
if (index >= 0) this.splice(index, 1);
return this;
};
var arr = ["orange","red","black","white"];
var arr2 = arr.deleteElem("red");

My approach, let's see what others have to say. It supports an "equals" method as well.
// Remove array value
// #param {Object} val
Array.prototype.removeByValue = function (val) {
for (var i = 0; i < this.length; i++) {
var c = this[i];
if (c == val || (val.equals && val.equals(c))) {
this.splice(i, 1);
break;
}
}
};
Read https://stackoverflow.com/a/3010848/356726 for the impact on iterations when using prototype with Array.

Or simply check all items, create a new array with non equal and return it.
var arr = ['orange', 'red', 'black', 'white'];
console.info('before: ' + JSON.stringify(arr));
var deleteElem = function ( val ) {
var new_arr = [];
for ( var i = 0; i < this.length; i++ ) {
if ( this[i] !== val ) {
new_arr.push(this[i]);
}
}
return new_arr;
};
arr = deleteElem('red');
console.info('after: ' + JSON.stringify(arr));
http://jsfiddle.net/jthavn3m/

The best way is to use splice and rebuild new array, because after splice, the length of array does't change.
Check out my answer:
function remove_array_value(array, value) {
var index = array.indexOf(value);
if (index >= 0) {
array.splice(index, 1);
reindex_array(array);
}
}
function reindex_array(array) {
var result = [];
for (var key in array) {
result.push(array[key]);
}
return result;
}
example:
var example_arr = ['apple', 'banana', 'lemon']; // length = 3
remove_array_value(example_arr, 'banana');
banana is deleted and array length = 2

If order the array (changing positions) won't be a problem you can solve like:
var arr = ["orange","red","black","white"];
arr.remove = function ( item ) {
delete arr[item];
arr.sort();
arr.pop();
console.log(arr);
}
arr.remove('red');
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

Here you go:
arr.deleteElem = function ( val ) {
for ( var i = 0; i < this.length; i++ ) {
if ( this[i] === val ) {
this.splice( i, 1 );
return i;
}
}
};
Live demo: http://jsfiddle.net/4vaE2/3/
The deleteElem method returns the index of the removed element.
var idx = arr.deleteElem( 'red' ); // idx is 1

javascript search array of arrays

Let's say we have the following js array
var ar = [
[2,6,89,45],
[3,566,23,79],
[434,677,9,23]
];
var val = [3,566,23,79];
Is there a js builtin function or jQuery one with which you can search the array ar for val?
Thanks
***UPDATE*************
Taking fusion's response I created this prototype
Array.prototype.containsArray = function(val) {
var hash = {};
for(var i=0; i<this.length; i++) {
hash[this[i]] = i;
}
return hash.hasOwnProperty(val);
}

you could create a hash.
var ar = [
[2,6,89,45],
[3,566,23,79],
[434,677,9,23]
];
var hash = {};
for(var i = 0 ; i < ar.length; i += 1) {
hash[ar[i]] = i;
}
var val = [434,677,9,23];
if(hash.hasOwnProperty(val)) {
document.write(hash[val]);
}

You can also use a trick with JSON serializing. It is short and simple, but kind of hacky.
It works, because "[0,1]" === "[0,1]".
Here is the working demo snippet:
Array.prototype.indexOfForArrays = function(search)
{
var searchJson = JSON.stringify(search); // "[3,566,23,79]"
var arrJson = this.map(JSON.stringify); // ["[2,6,89,45]", "[3,566,23,79]", "[434,677,9,23]"]
return arrJson.indexOf(searchJson);
};
var arr = [
[2,6,89,45],
[3,566,23,79],
[434,677,9,23]
];
document.body.innerText = arr.indexOfForArrays([3,566,23,79]);

function indexOfArray(val, array) {
var hash = {};
for (var i = 0; i < array.length; i++) {
hash[array[i]] = i;
}
return (hash.hasOwnProperty(val)) ? hash[val] : -1;
};
I consider this more useful for than containsArray(). It solves the same problem (using a hash table) but returns the index (rather than only boolean true/false).

Can you try this?
var ar = [
[2,6,89,45],
[3,566,23,79],
[434,677,9,23]
];
var val = [3,566,23,79];
var sval = val.join("");
for(var i in ar)
{
var sar = ar[i].join("");
if (sar==sval)
{
alert("found!");
break;
}
}

Why don't you use javascript array functions?
function filterArrayByValues(array, values) {
return array.filter(function (arrayItem) {
return values.some(function (value) {
return value === arrayItem;
});
});
}
Or if your array is more complicated, and you want compare only one property but as result return whole object:
function filterArrayByValues(array, values, propertyName) {
return array.filter(function (arrayItem) {
return values.some(function (value) {
return value === arrayItem[propertyName];
});
});
}
More about used functions: filter() and some()

You can use Array.prototype.some(), Array.prototype.every() to check each element of each array.
var ar = [
[2, 6, 89, 45],
[3, 566, 23, 79],
[434, 677, 9, 23]
];
var val = [3, 566, 23, 79];
var bool = ar.some(function(arr) {
return arr.every(function(prop, index) {
return val[index] === prop
})
});
console.log(bool);

I guess there is no such JS functionality available. but you can create one
function arrEquals( one, two )
{
if( one.length != two.length )
{
return false;
}
for( i = 0; i < one.length; i++ )
{
if( one[i] != two[i] )
{
return false;
}
}
return true;
}

The problem with this is that of object/array equality in Javascript. Essentially, the problem is that two arrays are not equal, even if they have the same values. You need to loop through the array and compare the members to your search key (val), but you'll need a way of accurately comparing arrays.
The easiest way round this is to use a library that allows array/object comparison. underscore.js has a very attractive method to do this:
for (var i = 0; i < ar.length; i++) {
if (_.isEqual(ar[i], val)) {
// value is present
}
}
If you don't want to use another library (though I would urge you to -- or at least borrow the message from the Underscore source), you could do this with JSON.stringify...
var valJSON = JSON.stringify(val);
for (var i = 0; i < ar.length; i++) {
if (valJSON === JSON.stringify(ar[i]) {
// value is present
}
}
This will almost certainly be significantly slower, however.

You can use toString convertion to compare elements
var ar = [
[2,6,89,45],
[3,566,23,79],
[434,677,9,23]
];
var val = [3,566,23,79];
s = !ar.every(a => (a.toString() != val.toString()));
console.log(s) // true

Use this instead
if (ar.join(".").indexOf(val) > -1) {
return true;
} else {
return false;
}

Use lodash isEqual
const isValIncludedInAr = ar.some(element => isEqual(element, val))

const arrayOne = [2,6,89,45];
const arrayTwo = [3,566,23,79];
const arrayThree = [434,677,9,23];
const data = new Set([arrayOne, arrayTwo, arrayThree]);
// Check array if exist
console.log( data.has(arrayTwo) ); // It will return true.
// If you want to make a set into array it's simple
const arrayData = [...data];
console.log(arrayData); // It will return [[2,6,89,45], [3,566,23,79], [434,677,9,23]]