I have always wondered this and every now and again it pops up.
var name = document.title;
var user = document.getElementsByClassName("class-name")[0].children[j].getElementsByTagName("a")[0].innerHTML;
var someArr = [];
for (var j = 0; j < document.getElementsByClassName("class-name")[0].children.length; j++) {
if (user == name) {
someArr.push(user)
};
};
alert(someArr);
Now this is all made up (obviously) but see how the variable "user" is checking for children[j], well if I were to try use this code, it would come up with an error along the lines of "Cannot read property 'getElementsByTagName' of undefined". Now my question is: Is there a way to allow this code to work without giving an error message and not executing. I would use this for clean code in the if loop, like all variables are used for. This wouldn't be the only instance of the "user" variable being used either so it is very useful.
Thanks in advance,
Daniel.
Your j variable will have undefined value if you use it before the for loop.
You could put it inside a function closure, but using variables like this does not make code readable in my opinion. What you can do is create a getUser() function and also cache the array of elements. Something like this:
var name = document.title;
var getUser = function(elem) {
return elem.getElementsByTagName('a')[0].innerHTML;
};
var initialArr = document.getElementsByClassName("class-name")[0].children;
var someArr = [];
for (var j = 0; j < initialArr.length; j++) {
var user = getUser(initialArr[j]);
if (user == name) {
someArr.push(user)
};
};
alert(someArr);
Related
gameI created the following "class":
function State(){
this.board = [];
for (i=0; i< 9; i++){
var row = [];
for (j=0; j< 9; j++){
row.push(0);
}
this.board.push(row);
}
}
It has a method called nextEmptyCell:
State.prototype.nextEmptyCell = function(){
...
}
I created an instance of this class and passed it to another function.
game = new State();
function solveSudoku(game){
var next = game.nextEmptyCell();
...
}
On the following line: var next = game.nextEmptyCell(); I receive an error saying:
"Uncaught TypeError: Cannot read property 'nextEmptyCell' of undefined".
I don't understand why 'game' is undefined and how to fix this error.
Link to the full code: jsfiddle.net/py6kv7ps/5
P.S. Is there a better way of using JS as OOP?
Issue comes from solveSudoku(), you are calling it recursively without passing an argument. Thats why you are getting error.
"Uncaught TypeError: Cannot read property 'nextEmptyCell' of
undefined".
function solveSudoku(game) {
if (solveSudoku(ADD game OBJECT HERE)) {
return game;
}
}
You probably meant game.nextEmptyCell(), not state.nextEmptyCell(). There is no variable named state anywhere in the code you posted.
Its because your parameter game shadows the glbal variable game of the same name. The global variable game = new State(); has the correct value. So you can pass it to your method call to use the correct value of game within the method solveSudoku()
function State(){
this.board = [];
for (i=0; i< 9; i++){
var row = [];
for (j=0; j< 9; j++){
row.push(0);
}
this.board.push(row);
}
}
State.prototype.nextEmptyCell = function(){
console.log('egvse gtrs');
document.write('egvse gtrs');
};
var game = new State();
function solveSudoku(game){
var next = game.nextEmptyCell();
}
solveSudoku(game);
This may seem like a duplicate question, and to some extent, it is, but I have already been through many similar questions, and sadly, none have suited my need. I would really appreciate problem-specific advice.
My main problem in the JavaScript code here is that I cannot access the values in the variables RememberText20 and RememberFullText, in function TextLimiter, from function ReadMoreLessText. The "Message" is an argument for the ReadMoreLessText function, which essentially matches the element clicked to the correct value in the aforementioned variables, which are themselves arrays.
*I know there is nothing wrong with the arrays themselves, as they retain their values as they are supposed to, because a simple alert() proves this. Similarly, there is nothing wrong with the Message argument, as the function ReadMoreLessText works fine with other values.
My simple problem is that I cannot access the values in the aforementioned variables, from the ReadMoreLessText function, although they are global variables, as they should be.
I would really appreciate a problem-specific answer here. Thank you in advance.
// JavaScript Document
//Start Text250
window.onload = function TextLimiter() {
for (y = 0; y < 6; y++) {
FullText = document.getElementsByClassName("Introduction")[y].innerHTML;
TextLength = FullText.length;
RememberFullText = [];
RememberFullText[y] = FullText;
var Text250 = FullText.substr(0, 250) + "...";
RememberText250 = [];
RememberText250[y] = Text250;
if (TextLength > 250) {
document.getElementsByClassName("Read_More")[y].innerHTML = "Read More→";
document.getElementsByClassName("Introduction")[y].innerHTML = Text250;
} else {
document.getElementsByClassName("Read_More")[y].innerHTML = "";
}
}
};
//End Text250
//Start ReadMoreLessText
var ReadMore = function(Message) {
var ScreenText = document.getElementsByClassName("Introduction")[Message].innerHTML;
if (ScreenText === RememberText250[Message]) {
document.getElementsByClassName("Introduction")[Message].innerHTML = RememberText250[Message];
} else {
document.getElementsByClassName("Introduction")[Message].innerHTML = RememberText250[Message];
}
};
//End ReadMoreLessText
Try defining RememberFullText and RememberText250 outside the enclosing for loop.
window.onload = function TextLimiter() {
RememberFullText = [];
RememberText250 = []
for (y = 0; y < 6; y++) {
...
As written they are set to an empty array in each iteration of the loop. Hence only the last entry of each array will be retained after the loop has finished.
I don't see your variables declared as globals. Do you have a var RememberText20, RememberFullText; outside any function?
ok i am trying to run the following code and i am getting back an exception that startsWith method is undefined. shouldnt this automatically be defined within javascript?
var mailArchive = retrieveMails();
var livingCats = {"Spot": true};
for (var mail = 0; mail < mailArchive.length; mail++) {
var paragraphs = mailArchive[mail].split("\n");
for (var paragraph = 0;
paragraph < paragraphs.length;
paragraph++) {
if (startsWith(paragraphs[paragraph], "born")) {
var names = catNames(paragraphs[paragraph]);
for (var name = 0; name < names.length; name++)
livingCats[names[name]] = true;
}
else if (startsWith(paragraphs[paragraph], "died")) {
var names = catNames(paragraphs[paragraph]);
for (var name = 0; name < names.length; name++)
delete livingCats[names[name]];
}
}
}
show(livingCats);
Some versions of javascript (an experimental method in Firefox) have a .startsWith() string method that you would use like:
if (paragraphs[paragraph].startsWith("died"))
Regular javascript does not have a global function startsWith() like you are trying to use so unless you're loading some library that has that function in it, that's why the browser is telling you it's undefined.
A recommended solution that would work in any version of JS, would be:
if (paragraphs[paragraph].indexOf("died") === 0)
instead.
Or, you could define the global function you're using:
function startsWith(src, find) {
return src.substr(0, find.length) == find;
}
It's a method of String, not a global function.
It should be:
paragraphs[paragraph].startsWith("born")
I have a function which works just fine the first if I call it just once, but when I call it repeatedly within a for loop, I get the following error:
TypeError: getNamedRange is not a function, it is string.
Doing a search on this error gives me a clue that this is a javascript error, not a Google Apps Script error. I haven't worked much with javascript, but I suspect it may have something to do with how I return the value from the function.
This is the code which calls the function:
var ss = SpreadsheetApp.getActiveSpreadsheet();
var baseSheet = ss.getSheetByName("Base");
var catCol = 9;
var riskAreaColumn = 10;
var numRows = baseSheet.getDataRange().getNumRows();
// I am not using this var, should I be?
var data = baseSheet.getDataRange().getValues();
var cell;
var rangeName;
var range;
var rule;
for(var i=2; i<numRows; i++){
cell = baseSheet.getRange(i, riskAreaColumn);
rangeName = getNamedRange("CategoryRiskRange",baseSheet.getRange(i, catCol).getValue());
range = SpreadsheetApp.getActiveSpreadsheet().getRangeByName(rangeName);
rule = SpreadsheetApp.newDataValidation().requireValueInRange(range).build();
cell.setDataValidation(rule);
}
SpreadsheetApp.flush();
}
This is the function being called:
function getNamedRange(categoryRange, category) {
var categoryList = SpreadsheetApp.getActive().getRangeByName(categoryRange).getValues();
for (var i = 0; i < categoryList.length; i++) {
if (categoryList[i][0] == category) {
getNamedRange = categoryList[i][1];
return getNamedRange;
}
}
}
The first time through the for loop works, the second time gives me the aforementioned error. Thank you for reading this, I hope it's clear.
you are overwriting the function definition here:
getNamedRange = categoryList[i][1];
this will work:
if (categoryList[i][0] == category) {
return categoryList[i][1];
}
Javascript doesn't interpret things until it gets to them, and is very happy to redefine things when you tell it to.
The first time through, it sees
function getNamedRange(categoryRange, category)
and says "oh, a function! Cool!" But in that function, you have the line
getNamedRange = categoryList[i][1];
and it says "Oh, so getNamedRange is something else now. Okay, I'm fine with that."
Rename your variable, and you should be fine.
function createTextFields(obj) {
for (var i = 0; i < obj.length; i++) {
var dataDump = {};
for (var key in obj[i]) {
var textField = Ti.UI.createTextField(pm.combine($$.labelBrown, {
left: 200,
height:35,
value:obj[i][key],
width:550,
keyboardType:Ti.UI.KEYBOARD_NUMBER_PAD,
layout:'horizontal',
backgroundColor:'transparent',
id:i
}));
dataDump[key] = textField.value;
var callback = function (vbKey) {
return function (e) {
dataDump[vbKey] = e.source.value;
};
}(key);
}
globalData.push(dataDump);
}
}
I am using the simlar code for Adding the data and it works fine. I posted the problem yesterday and it got resolved...
Last Object is always getting updated?
Now when i go to edit page, it shows me four text fields or number of text fields added... now when i edit something and click on save... the value get's updated on the fourth or the last TextFields Object...
Don't define functions inside loops. Computationally expensive and leads to problems, like this one. Here's a fix that should solve it:
function createTextFields(obj) {
var callback = function (vbKey, localDump) {
return function (e) {
localDump[vbKey] = e.source.value;
};
}
var i;
var max = obj.length;
for (i = 0; i < max; i++) {
var dataDump = {};
for (var key in obj[i]) {
dataDump[key] = textField.value;
var callBackInstance = function(keyn, dataDump);
}
globalData.push(dataDump);
}
}
JavaScript does not have block level scope, so your variables dataDump and callback, though "declared" inside for-loops actually belong to the function. As in, you're saving a value to dataDump, then you're overwriting it, each time you go through the loop. Which is why finally only the code that operated on the last value remains.
Take a look at What is the scope of variables in JavaScript? too.