I want to loop through something, and return true if at any point of loop, condition is met. If not met at all, then want to return false. How do I do this in Javascript.
Cant just write if and else, because only want the else to take care after finish looping all the options...
You can just do:
if(condition){
return true;
}
return false;
If I understand correctly, you're saying that you can't use else because you want to test all conditions, even if multiple of them are true?
If so, then you can use a variable to keep track of your return value, and then just return it at the end:
var result = false;
if (condition1) {
// ... whatever other logic you have ...
result = true;
}
if (condition2) {
// ... whatever other logic you have ...
result = true;
}
// ... etc. ...
return result;
Yes it can be done, return true when the condition is met and return false when the for loop has finished looping. Here is an example :
function my_function(array) {
for (var i = 0; i < array.length; i++) {
if (array[i] == 'my_test') {
return true;
}
}
return false;
}
if (x) { */ Do stuff and then eventually */ return true; }
if (y) { */ Do stuff and then eventually */ return true; }
if (z) { */ Do stuff and then eventually */ return true; }
...
return false;
If and only if none of the ifs are triggered, it will return false. If any of the ifs are triggered, it will return true within the if
Related
How do I break out of a jQuery each loop?
I have tried:
return false;
in the loop but this did not work. Any ideas?
Update 9/5/2020
I put the return false; in the wrong place. When I put it inside the loop everything worked.
To break a $.each or $(selector).each loop, you have to return false in the loop callback.
Returning true skips to the next iteration, equivalent to a continue in a normal loop.
$.each(array, function(key, value) {
if(value === "foo") {
return false; // breaks
}
});
// or
$(selector).each(function() {
if (condition) {
return false;
}
});
According to the documentation return false; should do the job.
We can break the $.each() loop [..] by making the callback function
return false.
Return false in the callback:
function callback(indexInArray, valueOfElement) {
var booleanKeepGoing;
this; // == valueOfElement (casted to Object)
return booleanKeepGoing; // optional, unless false
// and want to stop looping
}
BTW, continue works like this:
Returning non-false is the same as a continue statement in a for loop; it will skip immediately to the next iteration.
I came across the situation where I met a condition that broke the loop, however the code after the .each() function still executed. I then set a flag to "true" with an immediate check for the flag after the .each() function to ensure the code that followed was not executed.
$('.groupName').each(function() {
if($(this).text() == groupname){
alert('This group already exists');
breakOut = true;
return false;
}
});
if(breakOut) {
breakOut = false;
return false;
}
I created a Fiddle for the answer to this question because the accepted answer is incorrect plus this is the first StackOverflow thread returned from Google regarding this question.
To break out of a $.each you must use return false;
Here is a Fiddle proving it:
http://jsfiddle.net/9XqRy/
I know its quite an old question but I didn't see any answer, which clarify that why and when its possible to break with return.
I would like to explain it with 2 simple examples:
1. Example:
In this case, we have a simple iteration and we want to break with return true, if we can find the three.
function canFindThree() {
for(var i = 0; i < 5; i++) {
if(i === 3) {
return true;
}
}
}
if we call this function, it will simply return the true.
2. Example
In this case, we want to iterate with jquery's each function, which takes anonymous function as parameter.
function canFindThree() {
var result = false;
$.each([1, 2, 3, 4, 5], function(key, value) {
if(value === 3) {
result = true;
return false; //This will only exit the anonymous function and stop the iteration immediatelly.
}
});
return result; //This will exit the function with return true;
}
"each" uses callback function.
Callback function execute irrespective of the calling function,so it is not possible to return to calling function from callback function.
use for loop if you have to stop the loop execution based on some condition and remain in to the same function.
I use this way (for example):
$(document).on('click', '#save', function () {
var cont = true;
$('.field').each(function () {
if ($(this).val() === '') {
alert('Please fill out all fields');
cont = false;
return false;
}
});
if (cont === false) {
return false;
}
/* commands block */
});
if cont isn't false runs commands block
When submit the form it runs both means to say code inside if is running and after else code is also running.
$("#new_chq").submit(function(){
var inputs = document.getElementsByName("val_2[]");
var i;
for (i = 1; i <= inputs.length; i++) {
$('#file_'+i).each(function() {
if(!$('#file_'+i).val() == ''){
$('#text_'+i).attr('required', '');
return false;
}
else{
return true ;
}
});
}
});
As you can see in docs:
We can break the $.each() loop at a particular iteration by making the
callback function return false. Returning non-false is the same as a
continue statement in a for loop; it will skip immediately to the next
iteration.
So, you need to move the form event handling after the jQuery each-loop.
Here is an example:
$("#new_chq").on('submit', function() {
var isValid = true;
$('[id^=file_]').each(function() {
if($(this).hasAttr('required') && !$(this).val()) {
isValid = false;
return false; // <- this breaks the loop
};
});
return isValid;
});
Please note, there are other errors in your code, such as $('#file_'+i).each loop, which has no sense - that is one element with unique id.
How do I break out of a jQuery each loop?
I have tried:
return false;
in the loop but this did not work. Any ideas?
Update 9/5/2020
I put the return false; in the wrong place. When I put it inside the loop everything worked.
To break a $.each or $(selector).each loop, you have to return false in the loop callback.
Returning true skips to the next iteration, equivalent to a continue in a normal loop.
$.each(array, function(key, value) {
if(value === "foo") {
return false; // breaks
}
});
// or
$(selector).each(function() {
if (condition) {
return false;
}
});
According to the documentation return false; should do the job.
We can break the $.each() loop [..] by making the callback function
return false.
Return false in the callback:
function callback(indexInArray, valueOfElement) {
var booleanKeepGoing;
this; // == valueOfElement (casted to Object)
return booleanKeepGoing; // optional, unless false
// and want to stop looping
}
BTW, continue works like this:
Returning non-false is the same as a continue statement in a for loop; it will skip immediately to the next iteration.
I came across the situation where I met a condition that broke the loop, however the code after the .each() function still executed. I then set a flag to "true" with an immediate check for the flag after the .each() function to ensure the code that followed was not executed.
$('.groupName').each(function() {
if($(this).text() == groupname){
alert('This group already exists');
breakOut = true;
return false;
}
});
if(breakOut) {
breakOut = false;
return false;
}
I created a Fiddle for the answer to this question because the accepted answer is incorrect plus this is the first StackOverflow thread returned from Google regarding this question.
To break out of a $.each you must use return false;
Here is a Fiddle proving it:
http://jsfiddle.net/9XqRy/
I know its quite an old question but I didn't see any answer, which clarify that why and when its possible to break with return.
I would like to explain it with 2 simple examples:
1. Example:
In this case, we have a simple iteration and we want to break with return true, if we can find the three.
function canFindThree() {
for(var i = 0; i < 5; i++) {
if(i === 3) {
return true;
}
}
}
if we call this function, it will simply return the true.
2. Example
In this case, we want to iterate with jquery's each function, which takes anonymous function as parameter.
function canFindThree() {
var result = false;
$.each([1, 2, 3, 4, 5], function(key, value) {
if(value === 3) {
result = true;
return false; //This will only exit the anonymous function and stop the iteration immediatelly.
}
});
return result; //This will exit the function with return true;
}
"each" uses callback function.
Callback function execute irrespective of the calling function,so it is not possible to return to calling function from callback function.
use for loop if you have to stop the loop execution based on some condition and remain in to the same function.
I use this way (for example):
$(document).on('click', '#save', function () {
var cont = true;
$('.field').each(function () {
if ($(this).val() === '') {
alert('Please fill out all fields');
cont = false;
return false;
}
});
if (cont === false) {
return false;
}
/* commands block */
});
if cont isn't false runs commands block
I have my JavaScript code as:
$('[id^="thresholdParameter_"]').each(function(i, value) {
//any field is edited
if($(this).val() !== previousThresholdParameters[i]){
alert('Hello');
return true;
}
});
Here I want that once it reaches return true; it must come out of the function and return the true value. However, it it keeps on iterarting.
Why is it so? return in JavaScript does not function like return in Java??
Use return false instead of return true, as return true treated as continue and return false as break in $.each loop,
$('[id^="thresholdParameter_"]').each(function(i, value) {
//any field is edited
if($(this).val() !== previousThresholdParameters[i]){
alert('Hello');
return false; // use false
}
});
From $.each()
We can break the $.each() loop at a particular iteration by making the
callback function return false. Returning non-false is the same as a
continue statement in a for loop; it will skip immediately to the next
iteration.
Return false in each callback will only stop the each function.
See last example from jQuery each API: http://api.jquery.com/each/
You can try this:
var conditionMet = false;
$(selector).each(function() {
if (innerConditionMet) {
conditionMet = true;
return false; // stop the each
}
});
Try this since in your case it looks like you want to return true and used somewhere else:
var flag = false;
$('[id^="thresholdParameter_"]').each(function(i, value) {
//any field is edited
if($(this).val() !== previousThresholdParameters[i]){
alert('Hello');
flag = true;
return false;
}
});
var x = $('[id^="thresholdParameter_"]');
for(i in x){
if(x[i] !== previousThresholdParameters[i]){
alert('Hello');
return true; //
break;
}
}
retun false to break out of $.each()
try this fiddle for better understanding: http://jsfiddle.net/patelmilanb1/q348g/
<div class="number">
<h1>1</h1>
<h1>2</h1>
<h1>3</h1>
<h1>4</h1>
<h1>5</h1>
<h1>6</h1>
<h1>7</h1>
</div>
$('.number h1').each(function () {
var h1Value = $(this).text();
if (h1Value == 5) {
return false;
} else {
$(this).css("background-color", "#F1F1EF");
}
});
it will add background colour to all h1 untill it reaches number 5 and then breaks out of $.each loop
I have such code:
function allValid() {
$('input').each(function(index) {
if(something) {
return false;
}
});
return true;
}
which always returns true as return false; affects anonymous inner function. Is there an easy way to call outer function's return?
PS. I am not looking for a workaround, just want to know the answer to original question. If the answer is "not possible" it is fine.
Yeah, store it in a local variable.
function allValid() {
var allGood = true;
$('input').each(function (index) {
if (something) {
allGood = false;
}
});
return allGood;
}
You could also use Array.prototype.some which iterates until finding an element that matches the criteria.
function allValid() {
var inputs = $('input');
if(inputs.toArray().some(function(input){
if(something)
return true;
})) {
return false;
} else {
return true;
}
}
You can also do this with filter:
var anyInvalid = $('input').filter(function(index) {
if (inValidCheck)
return true;
}).length;
This works because 0 is treated as false, but it actually gives you the number of invalid, which you could use this to display "You have 3 invalid entries" or something if you wanted.
If you want to do this efficiently, I think this is the best way:
function allValid() {
elements = $('input')
for (i = 0; i < elements.length; i++) { invalidityCheck(elements[i]) && return false; }
return true;
}
Edit: Although a more JavaScript-y version would probably use exceptions:
function allValid() {
try
$('input').each(function(index)) {
if (something) { throw 'something happened!'; }
});
catch (e) {
if (e == 'something happened!') {
return false;
} else {
throw e;
}
}
return true;
}