I would like to use the same function on two different elements without duplicating my code and changing the id. I'd like to pass the ID as a parameter into my function but it's not working.
function getSelected(id){
var selected = new Array();
**var selObj = document.getElementById(id);** //The problem is here
var count = 0;
for (x=0; x<selObj.options.length; x++){
if (selObj.options[x].selected){
selected[count] = selObj.options.value;
count++;
}
}
alert(count)
}
Any ideas?
Looks to me as if the error is somewhere else, specificially in this line:
selected[count] = selObj.options.value;
Shouldn't that be:
selected[count] = selObj.options[x].value;
or (without the need for an extra "count" variable)
selected.push( selObj.options[x].value );
(Furthermore, you're missing a var in front of x = 0, thus making x a global variable.)
Related
I am trying to add event to all inputs, get the value (number) from those and insertHtml them into span elements.
This is my javascript code. I have no idea how to pass the variables.
var input_selector = document.querySelectorAll('.coins_n'); // input number elements
var price_selector = document.querySelectorAll('.price'); // span elements
for(var i = 0; i <= input_selector.length; i++) {
var input = input_selector[i];
var price = price_selector[i];
input.addEventListener('input', function(){
console.log(price); // not working
console.log(input); // not working
price.innerHTML = input.value; // not working
})
}
The problem here has to do with scoping of your variables. var is a weird one, whose scope isn't really limited to the block, but to the containing function. The following two are (essentially) the same:
var input;
var i = 0;
for(; i < input_selector.length; i++) input = input_selector[i];
and
for(var i = 0; i < input_selector.length; i++) var input = input_selector[i];
both create a variable named input in global scope, and then update that variable. That means that any functions that wants to read input later will just read the last version of input, and not the version at the time you defined the handler you would trigger later.
let, however, is block scoped, and your for loop is a block. So defining let input inside the for loop will mean that input is defined uniquely for every iteration of the loop, since every time the block gets executed a new scope is created for everything in there.
The same is true for var i = 0 in your for loop - any handler that calls it later will just log the last global value of i, but if you use let, that's not the case and every iteration of the loop has its own i. So your code could simply be reduced to this:
const input_selector = document.querySelectorAll('.coins_n');
const price_selector = document.querySelectorAll('.price');
for( let i = 0; i < input_selector.length; i++ ){
input_selector[i].addEventListener('input', event => {
price_selector[i].innerHTML = event.target.value;
});
}
This is pretty complex to explain once you start typing it out, so better read what other have already written at something like MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let
Ok. I've managed it by using let.
var input_selector = document.querySelectorAll('.coins_n');
var price_selector = document.querySelectorAll('.price');
for(var i = 0; i < input_selector.length; i++) {
let input = input_selector[i];
let price = price_selector[i];
input_selector[i].addEventListener('input', function(){
price.innerHTML = this.value;
})
}
It might be a beginner's question, but I can't seem to find an answer on this.
The data it is getting is data out of a JSon file. I want it to loop through all the rows it is seeing. The loop works how it is written below and returns me the info I need with the rest of the code. I am trying to create multiple variables like testVar1, testVar2, testVar3, .... I don't know if it is possible to do it this way, or if I need to find another solution.
var i = 0;
for (var x in data) {
var testVar1 = data[0][1]; // works
var testVar[i] = data[0][1]; // doesn't
i += 1;
}
How can I make the testVar[i] work ?
What is the correct syntax for this?
Your code misses the initialization of your array variable: var testVar = [];.
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Anyway, you may want to create those variables in the window object :
for (var i = 0; i <= 2; i++) {
name = 'var' + i;
window[name] = "value: " + i;
}
console.log(var0);
console.log(var1);
console.log(var2);
That way you can keep using the "short" variable name.
You can wrap all those variables in an object.
instead of:
var testVar1 = data[0][1];
Try:
var Wrapper = {};
//inside the for loop:
Wrapper["testVar" + i] = data[0][i];
...and so on.
You'd access them as Wrapper.testVar1 or Wrapper["testVar" + 1].
The problem you're having is pretty simple. You try to declare a variable as an array and in the same statement try to assign assign a value to a certain index. The reason this doesn't work is because the array needs to be defined explicitly first.
var testVar[i] = data[0][1];
Should be replaced with:
var testVar = []; // outside the loop
testVar[i] = data[0][1]; // inside the loop
Resulting in:
var i = 0,
testVar = [],
data = [
['foo', 'bar', 'baz'],
['kaas', 'is', 'baas']
];
for (var x in data) {
var testVar1 = data[0][1];
testVar[i] = data[0][1];
i += 1;
}
console.log('testVar1', testVar1);
console.log('testVar', testVar);
console.log('testVar[0]', testVar[0]);
console.log('testVar[1]', testVar[1]);
If i isn't an integer you should use an object instead. This can be seen in the answer of Tilepaper, although I advise against the use variables starting with a capital letter since they suggest a constant or a class.
Is there a way to loop a declaration of a variable? just a loop to help me declare the variables so i dont have to do the monotonous work of change the numbers of the variable
var height1 = document.getElementById('height1').value;
var height2 = document.getElementById('height2').value;
var height3 = document.getElementById('height3').value;
var height4 = document.getElementById('height4').value;
var height5 = document.getElementById('height5').value;
var height6 = document.getElementById('height6').value;
var height7 = document.getElementById('height7').value;
var height8 = document.getElementById('height8').value;
var height9 = document.getElementById('height9').value;
var height10 = document.getElementById('height10').value;
var height11 = document.getElementById('height11').value;
var height12 = document.getElementById('height12').value;
var height13 = document.getElementById('height13').value;
var height14 = document.getElementById('height14').value;
var height15 = document.getElementById('height15').value;
var height16 = document.getElementById('height16').value;
This is not a right way of coding that, Just do like,
var heights = [];
Array.from(document.querySelectorAll("input[id^=height]")).forEach(function(itm){
heights.push(itm.value);
});
And now you can iterate the array heights to manipulate the values as per your requirement.
The logic behind the code is, querySelectorAll("input[id^=height]") will select the input elements that has id starts with the text height. Since the return value of querySelectorAll is a nodelist, we have to convert it as an array before using array functions over it. So we are using Array.from(nodelist). That will yield an array for us. After that we are iterating over the returned array by using forEach and pushing all element's value into the array heights.
This is almost always an indication that you want an array. Something like this:
var heights = [];
for (var i = 1; i <= 16; i++) {
heights.push(document.getElementById('height' + i).value);
}
Then you can reference a value from the array with something like:
heights[1]
Though technically since in JavaScript your window-level variables are indexable properties of the window object, you can essentially do the same thing with variable names themselves:
for (var i = 1; i <= 16; i++) {
window['height' + i] = document.getElementById('height' + i).value;
}
Then you can still use your original variables:
height1
Though in the interest of keeping things outside of window/global scope, maintaining the array seems a bit cleaner (and semantically more sensible).
This seems to be a good use case for an object:
var heights = {};
for (var i = 1; i <= 16; i++) {
heights[i] = document.getElementById('height' + i).value;
}
Maybe its time to introduce function:
Generally speaking, a function is a "subprogram" that can be called by code external (or internal in the case of recursion) to the function. Like the program itself, a function is composed of a sequence of statements called the function body. Values can be passed to a function, and the function will return a value.
function getHeight(id) {
return document.getElementById(id).value;
}
Call with the wanted id and use it like a variable.
getHeight('height1')
Normally you would put them in an array.
var heights = []
for (i = 1; i < 17; i++) {
heights[i] = document.getElementById('height' + i).value;;
}
Beware this will give you a hole at the start of the array ie heights[0] has nothing in it. If you use this to iterate it won't matter...
for (var i in heights) {
alert(heights[i]);
}
I'm lookingfor a javascript function which returns the next value from an array on every function call.. I have created a script but i'm a little stuck now.. is there someone to help me?
My location:
resultLocation= "beugen";
This should be the identifier to get the correct array of id's. There will be more arrays with id''s for example resultLocation = "mill";
My array of Id's
var beugen = [];
beugen[0] = "140";
beugen[1] = "33";
beugen[2] = "121";
beugen[3] = "150";
beugen[4] = "52";
beugen[5] = "68";
beugen[6] = "70";
beugen[7] = "82";
beugen[8] = "15";
My function to return a value. (the next value should be shown on each call of getId (resultLoction)
getId = function(resultLocation) {
var arrayLength = beugen.length;
page = beugen;
for (var i = 0; i < arrayLength; i++) {
init_table(page[i]);
}
}
getId(resultLocation);
Now my function keeps on looping and calls the init_table(page[i]) as many times as there are id's in my array. It should get the first (140) on the first call of getId and the 2nd (33) on the next call, and if it reaches the end, it should start over again at the the top.
Maybe an array is not the best solution? I don't really know. Since there are multiple locations?
var i = -1;
function getId(){
i++;
if(i>beugen.length-1){
i=0;
}
init_table(beugen[i]);
return beugen[i];
}
or something like that might work if i understand the problem.
I'm having some trouble getting my code to work. This is what I have so far.
function outputNamesAndTotal() {
var name;
var outputTable;
var inputForm;
var nameArray;
var outputDiv;
outputDiv = document.getElementById("outputDiv");
inputForm = document.getElementById("inputForm");
outputTable = document.getElementById("outputTable");
name = inputForm.name.value;
nameArray = [];
nameArray.push(name);
for (var i = 0; i > nameArray.length; i++) {
outputTable.innerHTML += "<tr>" + nameArray[i] + "</tr>";
}
inputForm.name.focus();
inputForm.name.select();
return false;
}
When I add the loop it breaks the code completely, but I can't figure out why.
What I'm trying to do is use an HTML form to get a name from the user. Once the user enters the name, the program adds the name to the array, and outputs each array entry to a row in a table.
It's pretty basic, but it's still giving me all kinds of trouble!
I think you are clearing your array of names every time you call the function. You should bring the line:
nameArray = [];
out and make it global.
I ran a quick test and the following code works in at least FireFox
Edited to use appendChild
<html>
<head>
<script type='text/javascript'>
var names = [];
function addName() {
var nameTxt = document.getElementById('name_txt');
var name = nameTxt.value;
names.push(name);
var outTable = document.getElementById('out_tbl');
var row = document.createElement('tr');
var entry = document.createElement('td');
var txt = document.createTextNode(name);
entry.appendChild(txt);
row.appendChild(entry);
outTable.appendChild(row);
var numDiv = document.getElementById('num_div');
removeAllChildren(numDiv);
var numTxt = document.createTextNode('You have ' + names.length + ' names');
numDiv.appendChild(numTxt);
}
function removeAllChildren(e) {
while (e.hasChildNodes()) {
e.removeChild(e.firstChild);
}
}
</script>
</head>
<body>
<table id='out_tbl'>
</table>
<div id='num_div'>You have 0 names</div>
<input id='name_txt' type='text'/>
<button onclick="addName()">CLICK</button>
</body>
</html>
Edit: Oh yeah and you are the fact that you are looping through the array every time. If you "globalize" the name array, you're gonna print the whole array every time you add a name.
Edit x2: the code you originally posted had nameArray as a local variable inside the function. This effectively clears the array every time you call the function. Then every time you call the function you add the current name to the now empty array, and loop through all 1 (one) elements that the array now holds.
What you want to do is "globalize" the name array, and remove the loop from your function. This will allow you to build up your name array across multiple calls, and works the way that you want it.
Also, innerHTML is not really the best way to add things to the page. I would suggest using appendChild().
-C
for (var i = 0; i > nameArray.length; i++) {
I think you mean i < nameArray.length