How can I loop through a set of strings in Javascript? - javascript

I have a simple for loop that I need to set up. However instead of iterating through numbers I would like to iterate through:
"A", "B", "1" and then "2"
Is there a way I can do this with just creating an inline array?

As far as I understand, you would like to replace the usage of for() loop
var i;
var array = ["A", "B", "1", "2"];
for (i = 0; i < array.length; ++i) {
alert(array[i]);
}
You can do that by simply using forEach() function
var array = ["A", "B", "1", "2"];
array.forEach(function(value) {
alert(value);
});

Related

nested for each loop to insert value which in array without duplication and loop start from first

Example
If my values are in array like this
var myPlaces = ["a", "b", "c"];
var friendPlaces = ["d", "0", "e"];
for(var i = 0; i < myPlaces.length; i++) {
console.log(myPlaces[i]);
for(var j = 0; j < friendPlaces.length; j++) {
if (myPlaces[i] == friendPlaces[i]) {
console.log(myPlaces[i]);
};
I need answer as
(a,d)(b,0)(c,e) as three result but it gives count more than 3
help me to modify my current answer (a,d) (d,a) (d,b) (d,c) then (b,o)
You can use Array#map (Assuming your input arrays are of same length with fixed count of arrays- i.e. 2 in your case).
If you use map on myPlaces then 1st parameter is current value of myPlaces in loop and the 2nd parameter is index of that element in array. So you can match current element in myPlaces with elements from friendPlaces array with the same index using this index.
var myPlaces = ["a", "b", "c"];
var friendPlaces = ["d", "0", "e"];
var result = myPlaces.map((e, i) => "("+e +","+ friendPlaces[i]+")");
console.log(result);

How to remove element from array using javascript

I have 2 array and want to remove the elements of 2nd array as per position numbers on 1st array.
var notexists = []; //value is "1","5","8" on 0,1,2nd position.
var copyrequiredfields = [];//Value is "a","b","c","d","e","f",...
for (var i = 0; i < notexists.length; i++) {
copyrequiredfields.splice(parseInt(notexists[i]), 1);
}
as per example i want to remove 1st 5th and 8th element from copyrequiredfields .
Please suggest some answer.
Create a new array, iterate the copyrequiredfields, when the index in notexists, ignore it.
example:
var notexist = [1,2,5];
var copyrequiredfields = ['a','b','c','d','e','f','g'];
//create a index map
var index_map = {};
for(var i = 0; i < notexist.length; i++){
index_map[notexist[i]] = true;
}
//remove the elements
var newarray = [];
for(var i = 0; i < copyrequiredfields.length; i++){
if(!index_map[i]){
newarray.push(copyrequiredfields[i]);
}
}
copyrequiredfields = newarray;
In JS, index of array starts with 0 and not 1 so you just have to subtract 1 from value before splice. Rest of the code is fine.
One issue is, as you remove elements from array, elements after it are moved 1 position back. This will give you incorrect output. 1 hack is to count number of elements removed to count movement.
A better solution would be to use array.filter.
Array.splice
var notexists = ["1", "5", "8"]; //value is on 0,1,2nd position.
var copyrequiredfields = ["a", "b", "c", "d", "e", "f", "g", "h", "i"]; //Value is "a","b","c","d","e","f",...
var count=0;
for (var i = 0; i < notexists.length; i++) {
console.log(+notexists[i] - 1)
copyrequiredfields.splice(+notexists[i]-1-count++, 1);
}
console.log(copyrequiredfields)
Array.filter
var notexists = ["1", "5", "8"]; //value is on 0,1,2nd position.
var copyrequiredfields = ["a", "b", "c", "d", "e", "f", "g", "h", "i"]; //Value is "a","b","c","d","e","f",...
var r = copyrequiredfields.filter((x,i)=>notexists.indexOf((i+1).toString()) === -1)
console.log(r)
You could copy the whole array, except of the parts you dont need anymore:
var tempCopy = [];
for (var i=0; i < copyrequiredfields.length; i++)
if(notexists.indexOf(i)==-1)
tempCopy.push(copyrequiredfields[i]);
copyrequiredfields = tempCopy;
Greets!

Show array element on button click using javascript

I have an array of strings, you can see below and i want to alert each element one by one on button click:
function mysimplefunc() {
var i = 0;
var array = ["a", "b", "c", "d"];
if (array.length < 4)
{
var str = array[i];
i++;
alert(str);
}
}
below is asp code:
<asp:Button ID="btn_SHow" runat="server" Text="Show Elements" OnClientClick="mysimplefunc();" />
But its not working.
the if loop will not working since array length is 4
and u must use for loop inorder to iterate each element..!!
for ( i=0;i<array.length;i++)
{
var str = array[i];
alert(str);
}
Try this function. This handles creating the array counter (i) as a global variable, and any number of items can be included in the array, not just four.
function mysimplefunc() {
var array = ["a", "b", "c", "d"];
if (typeof i == "undefined") {i = 0};
alert(array[i++]);
if (i == array.length) {i = 0}
}
function mysimplefunc() {
var i = 0; //declare & initialise a integer variable used for loop counter.
var array = ["a", "b", "c", "d"]; //Create an string array of 4 elements with name array
var arrLength=array.length; //find the length of array elements
for (;i<arrLength;) //iterate over the array elements upto last element
{
var str = array[i]; //take first element from array
i++; //increment the loop counter
alert(str);//popup the small window with values present in array
}
}

How might I return multiple arrays with equal values from a larger array with mixed values?

I have an array that after being sorted appears like this:
var arr = ["a", "a", "b", "b", "b", "b", "c", "c", "c"];
There are 2 "a" Strings, 4 "b" Strings, and 3 "c" Strings.
I am trying to return 3 separate arrays, returning them one at a time from a loop, containing only matching values. So, upon the first iteration, the returned array would appear as newArr = ["a", "a"], the second as newArr = ["b", "b", "b", "b"] and on the third iteration as newArr = ["c", "c", "c"].
However, this is a small array of predefined values, and I need an algorithm that can perform the same operation on an array of unknown size, unknown elements, and with an unknown number of like elements. (and keep in mind that the array is already sorted to begin with, in this context)
Here's my crazy code that is displaying some unusual, and incorrect, results:
var arr = ["a", "a", "b", "b", "b", "b", "c", "c", "c"];
for(var index = 0; index < arr.length; index++)
{
var test = "";
var newArr = []; // resets the new array upon each iteration
var str = arr[index]; // initialized as the next unique index-value
for(var i = index; i < arr.length; i++)
{
if(arr[i] == str)
{
newArr.push(arr[k]);
test += arr[i] + " ";
}
else
{
index = i; // changing the outer loop variable
break; // exiting the inner loop
}
} // end of inner loop
window.alert(test);
setValues(newArr);
} // end of outer loop
function setValues(arrSorted)
{
var here = document.getElementById("here");
for(var i = 0; i < arrSorted.length; i++)
{
here.innerHTML += arrSorted[i] + " ";
}
here.innerHTML += "<br />";
} // end of setValues function
var arr = ["a", "a", "b", "b", "b", "b", "c", "c", "c"];
var arrays = {};
for (var i=0;i<arr.length;i++) {
if (!arrays[arr[i]]) arrays[arr[i]] = [];
arrays[arr[i]].push(arr[i]);
}
this will give you the equivalent of
arrays = {};
arrays['a'] = ['a','a'];
arrays['b'] = ['b','b','b','b','b'];
arrays['c'] = ['c','c','c'];
You can use a function like this to divide the array into several arrays:
function divide(arr) {
var subArrays = [];
var current = null;
var subArray = null;
for (var i = 0; i < arr.length; i++) {
if (arr[i] != current) {
if (subArray != null) subArrays.push(subArray);
current = arr[i];
subArray = [];
}
subArray.push(arr[i]);
}
if (subArray != null) subArrays.push(subArray);
return subArrays;
}
Demo: http://jsfiddle.net/Guffa/d8CBD/
This is how I would do it:
var arr = ["a", "a", "b", "b", "b", "b", "c", "c", "c"];
var out = [], prev;
for (var i = 0, j = 0, len = arr.length; i < len; i++) {
if (arr[i] !== prev || !out.length) {
out[j++] = [prev = arr[i]];
} else {
out[j - 1].push(prev);
}
}
//out -> [["a","a"],["b","b","b"],["c","c","c"]]
Demo
Note: the || !out.length check is just handle arrays that start with undefined correctly, but feel free to remove it if this will never be the case

Accessing objects within objects

var data = {
row: row,
row2: row2
};
var tableData = [data.row,data.row2];
row objects contains lot of children objects too... now how would i placed my tableData to access each single objects. so it goes like this...
var tableData = [data.row[1],data.row[2],data.row[3],,data.row2];
Updated Question
var data = [row, row2];
In this case how would i access my row children objects.
var data = {key: value, ... };
var tableData = [];
for (var k in data) {
for (var i = 0, len = data[k].length; i < len; i++)) {
tableData.push(data[k][i]);
}
}
Use nested for loops and array.prototype.push
Edit
for (var j = 0, len = data.length;j < len;j++) {
for (var i = 0, len = data[j].length; i < len; i++)) {
tableData.push(data[j][i]);
}
}
You can replace for (var j in data) with for (var j = 0, len = data.length; j < len; j++)
The latter
sets j to 0
caches the length so you only ask for the length once.
Checks that j is not bigger then the amount of elements in your array
Increases j when you get to the end of the block.
Assign data.row first, then push data.row2, like this:
var tableData = data.row
tableData.push(data.row2)
How about something like this...
var data = {
letters : ["a", "b", "c"],
numbers : ["0", "1", "2", "3"]
};
data.letters; // ["a", "b", "c"]
data.letters[0]; // "a"
data.numbers; // "0", "1", "2", "3"]
data.numbers[2]; // "2"
... or you could try this...
var data = {
letters : new Array("a", "b", "c"),
numbers : new Array("0", "1", "2", "3")
};
data.letters; // ["a", "b", "c"]
data.letters[0]; // "a"
data.letters.push("d"); // the array is now ["a", "b", "c"]
data.numbers; // ["0", "1", "2", "3"]
data.numbers[2]; // "2"
data.numbers.pop(); // the array is now ["0", "1", "2"]
For more info on JavaScript arrays, check out these links:
http://www.hunlock.com/blogs/Mastering_Javascript_Arrays
http://blog.xkoder.com/2008/07/10/javascript-associative-arrays-demystified/
I hope this helps.
Hristo

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