I have a set of variables:
var var1 = 0;
var var2 = 0;
var var3 = 0;
var var4 = 0;
var var5 = 0;
And I want to check them all with a for Loop, but I'm not quite sure of the syntax:
for( var i = 1; i<6; i++){
alert(var[i]);
}
that for loop yields no results.
Put them in an array instead.
var vars = [0, 0, 0, 0, 0, 0];
for(var i = 0; i < vars.length; i++) {
alert(vars[i]);
}
If you're defining the varables in the global scope, you can access the values using window['var'+i]:
for(var i = 1; i<6; i++){
alert(window['var'+i]);
}
To access them you would have to use the scope to which they were written. If your code is in the window scope that would then become:
for( var i = 1; i<6; i++){
alert(window['var'+i]);
}
Though of course it's far cleaner if it's in a different scope specific to whatever you're doing. In those cases often
for( var i = 1; i<6; i++){
alert(this['var'+i]);
}
would work.
The data construct you are using is not good for this. Using an array or object is much more feasible for what you want to do as well as being easily extendable.
var arr = [0,0,0,0,0,0];
for (var i = 0; i < arr.length; i++) {
alert(arr[i]);
}
var[i] is used it var is an array. But in your case it isn't. The best way would be to place those values in an array, like;
var myvar = [0,0,0,0,0];
then use the for loop to check for the value.
for( var i = 1;i<6; i++){
alert(myvar[i-1]);
}
Related
I want to create new variables in a for-loop where the variable-name shall contain the index of the loop: pos_1, pos_2...
So I try that:
for(i=1; i<=slide_length;i++){
var pos_[i] = 49*i;
}
But that doesn't create anything. What do I do wrong here?
You can use window["variable_name"] to create global variables.
var slide_length = 5;
for(i=1; i<=slide_length;i++){
window["pos_"+i] = 49*i;
}
console.log(pos_5);
create the array outside the loop.
var pos_ = []
for(i=1; i<=slide_length;i++){
pos_.push(49*i);
}
then pos_ has your values after the loop.
You should use an array:
function createVariables(){
var pos = [];
for (var i = 0; i <= slide_length; ++i) {
pos[i] = 49*i;
}
return pos;
}
You then have access to pos[0] through pos[slide_length].
Following code will be useful to you,
var slide_length = 10;
for(i=1; i<=slide_length;i++){
this['pos_'+i] = 49 * i;
}
console.log(pos_1);
console.log(pos_8);
console.log(pos_10);
my question is can i possibly initialize variables repeatedly (with changing only numbers after them) this is my code
for(i = truStorage.getItem('elementCount'); i>0; i--) {
var obj = truStorage.getItem("element_" + i);
var [obj_+i] = element(erd.Entity , obj.posx, obj.posy, obj.text );}
};
basically i just want to initialize a variable like
something_i = "";
and the result will be like this
var element_1 = element(erd.Entity, 100, 200, "Employee");
var element_2 = element(erd.Entity, 100, 400, "Salesman");
var element_3 = element(erd.WeakEntity, 530, 200, "Wage");
var element_4 = element(erd.IdentifyingRelationship, 350, 190, "gets paid");
im not trying to use variables as a storage but rather to instantiate an element for a function.
This is a job for an array.
var something = [];
var somethings = 5;
for(var i = 0; i < somethings; i++) {
something[i] = "";
}
You should now be able to access the five values like this:
console.log(something[0])
console.log(something[1])
console.log(something[2])
console.log(something[3])
console.log(something[4])
Notice you use 0 to access the first element. That's just how it is because JavaScript arrays are zero-based.
This is best scenario to use array:
var counter=0,something = new Array();
for(i = truStorage.getItem('elementCount'); i>0; i--) {
something[counter] = truStorage.getItem("element_" + i).text;
counter++;
}
};
Try:
for(var i=1; i<=4; i++) {
this["something_" + i] = i;
}
console.log(something_1); //outputs 1;
console.log(something_2); //outputs 2;
console.log(something_3); //outputs 3;
console.log(something_4); //outputs 4;
Note: using an array will be faster!
I have the following javascript
information0 = xmlDoc.getElementsByTagName("info")[0].textContent;
information1 = xmlDoc.getElementsByTagName("info")[1].textContent;
information2 = xmlDoc.getElementsByTagName("info")[2].textContent;
information3 = xmlDoc.getElementsByTagName("info")[3].textContent;
information4 = xmlDoc.getElementsByTagName("info")[4].textContent;
information5 = xmlDoc.getElementsByTagName("info")[5].textContent;
information6 = xmlDoc.getElementsByTagName("info")[6].textContent;
I want to create a new var for each index number. There are 600 in total. How can I do this using a for loop?
Thanks in advance
The best thing here is to use an array, not a bunch of individual variables.
var information = [];
var index;
var info = xmlDoc.getElementsByTagName("info");
for (index = 0; index < info.length; ++index) {
information[index] = info[index].textContent;
}
Um... use an array? Also, don't call getElementsByTagName repeatedly, it's expensive!
var tags = xmlDoc.getElementsByTagName('info'), l = tags.length, i, information = [];
for( i=0; i<l; i++) information[i] = tags[i].textContent;
If you're in a reasonably up-to-date browser:
var information = [].map.call(xmlDoc.getElementsByTagName('info'),function(a) {return a.textContent;});
Like this:
var information = [],
i,
elements = xmlDoc.getElementsByTagName("info"),
n = elements.length;
for (i = 0; i < n; ++i) {
information[i] = elements[i].textContent;
}
You need to use an array.
var infoTags = xmlDoc.getElementsByTagName("info"),
i = 0,
len = infoTags.length,
values = []; //array literal syntax, you could also use new Array()
for (; i < len; i++) {
values.push(infoTags[i].textContent); //push the textContent into the array
}
Things that you should note:
I cached the result of getElementsByTagName instead of performing the query multiple times.
I cached the length property of infoTags. That avoids multiple property lookups to access infoTags.length on every iterations. Property lookups are expensive in JavaScript.
To know how you can work with arrays, have a look at the Array object.
-
This may be a fairly simple question but it's just not working for me no matter how many times I change the for loop around. So how would you loop through this array using a for loop in JavaScript?
var fielditems =[
[["News Tips"],["Opinions"],["MedMinutes"]],
[["Yes"],["No"],["Maybe"]],
[["How"],["Why"],["When"]]
];
This is what I have and it's not working. I used an alert to just test out the result but it's not even returning anything.
for(itemSet in fielditems){
var itemSetValues = fielditems[itemSet];
for(set in itemSetValues){
var itemValue = itemSetValues[set];
for(value in itemvalue){
alert(itemValue[value]);
}
}
}
What am I doing wrong?
Don't use for() with in for arrays. It's for object properties. Use the standard format instead.
Demo: http://jsfiddle.net/ThinkingStiff/EVWch/
Script:
var fielditems =[
[["News Tips"],["Opinions"],["MedMinutes"]],
[["Yes"],["No"],["Maybe"]],
[["How"],["Why"],["When"]]
];
for( var itemIndex = 0; itemIndex < fielditems.length; itemIndex++ ){
var itemSetValues = fielditems[itemIndex];
for(var setIndex = 0; setIndex < itemSetValues.length; setIndex++ ){
var itemValue = itemSetValues[setIndex];
for(var valueIndex = 0; valueIndex < itemValue.length; valueIndex++ ){
alert(itemValue[valueIndex]);
};
};
};
Firstly, console is your friend. You get error ReferenceError: itemvalue is not defined because javascript is case sensitive. Change itemvalue in the most nested loop to itemValue.
Secondly, if you want iterate thorugh an array, you should use for-loop instead for-in-loop
Don't use for-in loops on arrays
Don't use (running) variables without declaring them as local
for (var i=0; i<fielditems.length; i++) {
var itemSetValues = fielditems[i];
for (var j=0; j<itemSetValues.length; j++) {
var itemvalue = itemSetValues[j]; // notice the case
for (var k=0; k<itemvalue.length; k++) {
alert(itemvalue[k]);
}
}
}
for..in is for objects ({}), not for arrays ([]).
You need to use a standard for loop.
for(var i = 0, iLen = fielditems.length; i < iLen; i++){
var iItem = fielditems[i];
for(var j = 0, jLen = iItem.length; j < jLen; j++){
var jItem = iItem[j];
alert(jItem[0]); // you can also add another loop here, if this will have more elements
}
}
NOTE:
for(var i = 0, iLen = fielditems.length; i < iLen; i++)
is better than:
for(var i = 0; i < fielditems.length; i++)
because fielditems.length isn't requested each loop, just once at the start.
is it possible to add i to a var inside a for-loop?
in wrong syntax it would look like the code below
for(i=1; i<=countProjects; i++){
var test + i = $(otherVar).something();
};
Thanks!
It would be best to use an array for this:
var test = [];
for (i = 1; i <= countProjects; i++) {
test[i] = $(otherVar).something();
};
Then you could access the values like this:
console.log(test[1]);
console.log(test[2]);
etc...
If you have really good reason to have named variables for each value, you can create them like this:
for (i = 1; i <= countProjects; i++) {
window["test" + i] = $(otherVar).something();
};
console.log(test1);
As Mat stated, you should be using arrays for this type of functionality:
var projects = [];
for (var i = 0; i <= countProjects; i++) {
projects.push($(otherVar).something());
}
You could craft variable names, using object["varname"] syntax. But it's _generally_ bad practice:
var varName;
for (var i = 0; i <= countProjects; i++) {
varName = "test" + i.toString();
this[varName] = $(otherVar).something();
}
console.log(test1);