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How To implement unshift method in Javascript

i need make function like this:
Function add(arr,...newVal){
}
array = [1,2,3];
add(array,0)
console.log(array); //i need here to print [0,1,2,3]
iam make function as push like that:
Function add(arr,...newVal){
for(var i=0; i<arr.length; i++){
arr[arr.length]=newVal[i];
}return arr.length;
}
array = [1,2,3];
add(array,4)
console.log(array); // here to print [1,2,3,4]

const unshift = (arr, ...newVal) => {
let i= arr.length + newVal.length -1;
for( i ; i >= newVal.length; i--) {
arr[i] = arr[i - newVal.length ];
}
for(i; i >= 0; i--) {
arr[i] = newVal[i];
}
return arr;
}

Try this:
const unshift = (arr, newVal) => {
for(let i = arr.length; i > 0; i--) {
arr[i] = arr[i - 1];
}
arr[0] = newVal;
return arr;
}

Return Sorted Array Without Modifying Original Array

I'm having trouble with a function returning the original array as opposed to the sorted array. I tried to slice the array and return the sorted but it is not working. Any ideas on how to fix this?
function sortArr( comparator, array ){
var newArray = array.slice();
for(var i = 0; i < newArray.size; i++)
{
var min = i;
for(var x = i; x < newArray.size; x++)
{
if(comparator(newArray[min],newArray[x]) == true)
{
min = x;
}
}
var temp = newArray[i];
newArray[i] = newArray[min];
newArray[min] = temp;
}
return newArray;
}
I fixed the function:
function sortArr( comparator, array ){
/*your code here*/
var i, x;
var min;
var newArray = array.slice();
for(i = 0; i < newArray.length - 1; i++)
{
min = i;
for(x = i + 1; x < newArray.length; x++)
{
if(comparator(newArray[min],newArray[x]) == true)
{
min = x;
}
}
if(min != i){
var temp = newArray[i];
newArray[i] = newArray[min];
newArray[min] = temp;
}
}
return newArray;
}

Copy the array with slice and then use native sort:
function sortArr(comparator, array) {
return array.slice().sort(function(a,b) {
return comparator(a,b) * 2 - 1;
});
}

Your sorting algorithm doesn't look quite right. For a start the swapping of values should be inside the if statement. I would also advise to look at #Oriol's solution which is far more elegant.
function sortArr( comparator, array ){
var newArray = array.slice();
for(var i = 0; i < newArray.size; i++)
{
var min = i;
for(var x = i; x < newArray.size; x++)
{
if(comparator(newArray[min],newArray[x]) == true)
{
var temp = newArray[i];
newArray[i] = newArray[min];
newArray[min] = temp;
min = x;
}
}
}
return newArray;
}

{"index.js":"var globalArray = [5, 6, 3, 2, 9];
function nonMutatingSort(arr) {
let newArr = globalArray.slice();\n let emptyArr = [];
return emptyArr.concat(newArr).sort();
}
nonMutatingSort(globalArray);"}

removing duplicate numbers out of both arrays

I know that you can remove 1 of the duplicate number out of an array but is there a way you can remove the number if they're duplicate? So far, below code is what I have. I wanted to use for loop to remove the number out of the array if they're equal, but I dont think I coded it correctly or it's not complete. I want it to return [3, 4, 5]
function sym(args) {
var array = [];
var join;
for(var i = 0; i < arguments.length; i++){
array.push(arguments[i]);
join = array[0].concat(array[1]);
}
join.sort();
for(var j = 0; j < join.length; j++) {
if(join[j] === join[j+1]) {
var removed = join.splice(j, join[j+2]);
console.log(removed);
}
}
return join;
}
sym([1, 2, 3], [5, 2, 1, 4]);

Here's my take
function sym() {
var vals = {};
var rarray= [];
var a=arguments;
for (var i=0,l=a.length;i<l;i++) {
if (a[i] instanceof Array) {
for (var n=0,ln=a[i].length;n<ln;n++) {
vals[a[i][n]]=vals[a[i][n]]||[];
vals[a[i][n]].push(a[i][n]);
}
}
}
for (var i in vals) {
if (vals.hasOwnProperty(i)) {
if (vals[i].length===1)
rarray.push(i);
}
}
return rarray;
}
Examples:
sym([1, 2, 3], [5, 2, 1, 4]);
// return: ["3", "4", "5"]
sym([1, 2, 3], [5, 2, 1, 4],[4,6,7,8],[8,4]);
// ["3", "5", "6", "7"]
sym([1,2],[1]);
// return: ["2"]

var sym = function (ar1, ar2) {
return ar1
.concat(ar2)
.sort(function (a, b) { return a - b; })
.filter(function (elem, i, ar) {
return ar[i-1] !== elem && ar[i+1] !== elem;
});
}

I like Crayon Violent's solution, but I don't see the point in maintaining arrays of duplicate items when you can simply count them.
This provides a large performance increase (jsperf), while also simplifying the code.
function sym() {
var occurrences = {};
var inputArrays = arguments;
var uniqueItems = [];
function addOccurrences(arr) {
for (var i = 0, len=arr.length; i < len; i++) {
occurrences[arr[i]] = 1 + (occurrences[arr[i]] || 0);
}
}
for (var i=0, len=inputArrays.length; i < len; i++) {
if (inputArrays[i] instanceof Array) {
addOccurrences(inputArrays[i]);
}
}
for (var item in occurrences) {
if (occurrences[item] === 1) {
uniqueItems.push(item);
}
}
return uniqueItems;
}
Which can be made nicer if you happen to have underscore or lodash in your project:
function sym() {
var inputArrays = _.filter(arguments, _.isArray);
var occurrences = {};
function addOccurrences(arr) {
_.forEach(arr, function(item){
occurrences[item] = 1 + (occurrences[item] || 0);
});
}
_.forEach(inputArrays, addOccurrences);
// Select the items with one occurence, return the keys (items)
return _.filter(_.keys(occurrences), function(item){
return occurrences[item] === 1;
});
}

Remove duplicate item from array Javascript [duplicate]

This question already has answers here:
Get all non-unique values (i.e.: duplicate/more than one occurrence) in an array
(97 answers)
Closed 8 years ago.
I'm looking for an easy way of removing a duplicate value from an array. I figured out how to detect if there is a duplicate or not, just I don't know how to "push" it from the value. For example, if you go to the link provided, and then type, "abca" (press return/enter key after each letter).. it will alert "duplicate!"
But I also want to figure out how to remove that duplicate from the textarea?
http://jsfiddle.net/P3gpp/
This is the part that seems to not be working ::
sort = sort.push(i);
textVal = sort;
return textVal;

Why do it the hard way, it can be done more easily using javascript filter function which is specifically for this kind of operations:
var arr = ["apple", "bannana", "orange", "apple", "orange"];
arr = arr.filter( function( item, index, inputArray ) {
return inputArray.indexOf(item) == index;
});
---------------------
Output: ["apple", "bannana", "orange"]

Based on user2668376 solution, this will return a new array without duplicates.
Array.prototype.removeDuplicates = function () {
return this.filter(function (item, index, self) {
return self.indexOf(item) == index;
});
};
After that you can do:
[1, 3, 3, 7].removeDuplicates();
Result will be; [1, 3, 7].

These are the functions I created/use for removing duplicates:
var removeDuplicatesInPlace = function (arr) {
var i, j, cur, found;
for (i = arr.length - 1; i >= 0; i--) {
cur = arr[i];
found = false;
for (j = i - 1; !found && j >= 0; j--) {
if (cur === arr[j]) {
if (i !== j) {
arr.splice(i, 1);
}
found = true;
}
}
}
return arr;
};
var removeDuplicatesGetCopy = function (arr) {
var ret, len, i, j, cur, found;
ret = [];
len = arr.length;
for (i = 0; i < len; i++) {
cur = arr[i];
found = false;
for (j = 0; !found && (j < len); j++) {
if (cur === arr[j]) {
if (i === j) {
ret.push(cur);
}
found = true;
}
}
}
return ret;
};
So using the first one, this is how your code could look:
function cleanUp() {
var text = document.getElementById("fld"),
textVal = text.value,
array;
textVal = textVal.replace(/\r/g, " ");
array = textVal.split(/\n/g);
text.value = removeDuplicatesInPlace(array).join("\n");
}
DEMO: http://jsfiddle.net/VrcN6/1/

You can use Array.reduce() to remove the duplicates. You need a helper object to keep track of how many times an item has been seen.
function cleanUp()
{
var textBox = document.getElementById("fld"),
array = textBox.value.split(/\r?\n/g),
o = {},
output;
output = array.reduce(function(prev, current) {
var key = '$' + current;
// have we seen this value before?
if (o[key] === void 0) {
prev.push(current);
o[key] = true;
}
return prev;
}, []);
// write back the result
textBox.value = output.join("\n");
}
The output of the reduce() step can be used directly to populate the text area again, without affecting the original sort order.
Demo

You can do this easily with just an object:
function removeDuplicates(text) {
var seen = {};
var result = '';
for (var i = 0; i < text.length; i++) {
var char = text.charAt(i);
if (char in seen) {
continue;
} else {
seen[char] = true;
result += char;
}
}
return result;
}
function cleanUp() {
var elem = document.getElementById("fld");
elem.value = removeDuplicates(elem.value);
}

arr3 = [1, 2, 3, 2, 4, 5];
unique = [];
function findUnique(val)
{
status = '0';
unique.forEach(function(itm){
if(itm==val){
status=1;
}
})
return status;
}
arr3.forEach(function(itm){
rtn = findUnique(itm);
if(rtn==0)
unique.push(itm);
});
console.log(unique); // [1, 2, 3, 4, 5]

Does jQuery have a method for checking all values of an array to see if they meet some criteria?

I'm looking for something similar to Groovy's every() method, which tests every element of a list if it meets some criteria. If they all meet the criteria, the function returns true. Otherwise, false. I've tried something like this:
var arr = [1, 0, 1, 0, 1, 1];
var allOnes = $.grep(arr, function(ind) {
return this == 1;
}).length == arr.length;
..but its not very clean. I haven't had any luck while searching through the API. Is using grep() the only way to do it?

if it is a plain js array, you have $.grep()
.filter() is for use with jQuery or DOM Elements

Here is a plugin I made that might make it easier:
(function($) {
$.fn.allOnes = function() {
var allVal = true;
this.each(function(ind, item) {
if (item != 1) {
allVal = false;
return allVal;
}
});
return allVal;
};
})(jQuery);
var arr = [1, 1, 0, 1, 1, 1];
console.log($(arr).allOnes());
Fiddle: http://jsfiddle.net/maniator/NctND/
The following plugin is an expansion of the above and lets you search for a specific number: http://jsfiddle.net/maniator/bFNnn/
(function($) {
$.fn.allValue = function(pred) {
var allOnes = true;
this.each(function(ind, item) {
if (item != pred) {
allOnes = false;
return allOnes;
}
});
return allOnes;
};
})(jQuery);
var arr = [1, 1, 1, 1, 1, 1];
console.log($(arr).allValue(1));

here is example of function you can use.
var arr = [1, 0, 1, 0, 1, 1];
var allOnes = arr.check(1);
//this function compares all elements in array and if all meet the criteria it returns true
Array.prototype.chack = function(cond)
{
var ln = 0;
for(i=0; i<this.length; i++)
{
if(bond === this[i])
{
ln++
}
}
if(ln == this.length)
return true;
else
return false;
}

How about just turning your working code into a method on array, to ease its reuse:
Array.prototype.every = function(predicate){
return $.grep(this,predicate).length == this.length;
}
usage:
alert([1,0,1,0].every(function(i) { return i == 1; }));
Working example: http://jsfiddle.net/59J5A/
Edit: changed to grep

You could always implement an allOnes method:
function allOnes(array) {
var result = [];
for(var i = 0; i < array.length; i += 1) {
if (array[i] === 1) { result.push(true); }
}
return array.length == result.length;
}
or you could be a bit more abstract and test for true/false:
function all(array) {
var result = [];
for(var i = 0; i < array.length; i += 1) {
if (array[i]) { result.push(true); }
}
return array.length == result.length;
}
var arr = [1, 0, 1, 0, 1, 1];
var allOnes = all(arr);
or even better, maybe have a changeable predicate:
function all(array, predicate) {
var result = [],
predicate = predicate || function(x) { if (x) { return true; } };
for(var i = 0; i < array.length; i += 1) {
if (predicate(array[i])) { result.push(true); }
}
return array.length == result.length;
}
var allOnes = all(arr, function(x) { return x === 1; })