I am trying to make an array of functions so that I can train a machine learning algorithm. One problem I am running into, for instance:
var fun = [String.prototype.split];
var str = 'test1&test2';
var result = str.fun[0]('&');
gives me the error of "cannot read property 0 of undefined". this is because the str does not have the literal fun array within itself to be called. Is the only way to correct this is to wrap every function such as the following or is there another way:
function splitter (str1, str2) {
return str1.split(str2);
}
var fun = [splitter];
var str = 'test&test';
var result = fun[0](str, '&');
If there is another way to do this I would really like to know as it will save me a lot of time wrapping every function like the above.
var arr = [String.prototype.split];
var str = 'test&test';
arr[0].call(str, '&');
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call
Related
I have tried everything and I can not split a PHP variable into two parts so I can insert them into two input fields. I have read numerous topics here and I don't see the problem...
This peace of code gives me a result that php variable is inserted into a wanted filed.
Lets say the PHP variable is data1-data2:
document.hiderad.selectstate.onchange = updateText;
function updateText() {
var str = document.hiderad.selectstate;
document.hiderad.opis.value = str.value;
}
Code above inserted data1-data2 into wanted HTML input.
And soon as i try to split it i get undefined warning. I have tried 7 different things to approach this problem so i want even list all the versions I tried. Can someone please help?
document.hiderad.selectstate.onchange = updateText;
function updateText() {
var str = document.hiderad.selectstate;
var array = str.toString().split('-');
a = array[0], b = array[1];
document.hiderad.opis.value = a.value;
document.hiderad.iznos.value = b.value;
}
Code above gives me b undefined if i remove last line i get a undefined.
You shouldn't be using a.value and b.value, that's for getting the value of an input field, not a string. You should use that to get the value of the selectstate input.
Also, always declare local variables unless you have a specific reason to assign global variables.
function updateText() {
var str = document.hiderad.selectstate;
var array = str.value.split('-');
var a = array[0], b = array[1];
document.hiderad.opis.value = a;
document.hiderad.iznos.value = b;
}
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.
Can I do something like this?
var mystring = "http%3A%2F%2Fstackoverflow.com%2F";
var mydecodedstring = mystring.apply(decodeURIComponent);
I know I can do this
var mydecodedstring = decodeURIComponent(mystring);
But I'd like to chain this if possible for syntactic purposes. Just curious if it's possible. My goal is:
mystring.?????
Your should see this to see how apply works. You could do something like:
var mystring = "http%3A%2F%2Fstackoverflow.com%2F";
var mydecodedstring = decodeURIComponent.apply(null, mystring);
Clearly, apply will not provide what you are looking for.
You could define your own function on the String prototype for decoding or define it only on your object.
maybe you want to add a new method to String object?
String.prototype.apply= function(entry){
return decodeURIComponent(entry);
}
var mystring = "http%3A%2F%2Fstackoverflow.com%2F";
var mydecodedstring = mystring.apply(decodeURIComponent);
So i've got this code below (all javascript). And I wish to grab the votecount for a game on user input
function Game(gamename,votes) {
this.gamename = gamename;
this.votes = votes;
};
var lol = new Game("League of Legends",1100);
var dota = new Game("DOTA 2",2100);
var ql = new Game("Quakelive",3100);
var csgo = new Game("Counter Strike: GO",4100);
function PostVotes(gnshort){
//string names - working
console.log(gnshort + 'name');
console.log(gnshort + 'votes')
var CalcVotes = function(gnshort){
var votecount = gnshort.votes;
console.log(votecount);
}
CalcVotes(gnshort);
//CalcVotes(lol); //works
};
PostVotes('lol');
I keep getting the error undefined when calling CalcVotes(gnshort). and I know it's not the function it's passing the lol as gnshort it's asif it's reading as a string instead of a variable or something. I've only been learning javascript for the past week so any advice would be helpful
PostVotes('lol'); will pass lol as a string ('lol' is equivalent to "lol"). What you need to do is simply pass the variable lol like
PostVotes(lol);
And it will return lol.votes, aka 1100.
I currently have a block like this defining some vars
var slider_1 = document.querySelector('#slider_1');
var slider_2 = document.querySelector('#slider_2');
...
And func's that take ID's like this:
function updateFromInput(id){
if(id==1){
var x = input_1.value*1;
x = Math.round((x*ratio)-offset);
slider_1.x.baseVal.value = x/scale;
}else if(id==2){
var x = input_2.value*1;
x = Math.round((x*ratio)-offset);
slider_2.x.baseVal.value = x/scale;
}
};
I am trying to refactor a bit.
I'm thinking that if I could, instead, instantiate my vars with dots rather than underscores like
var slider.1 = document.querySelector('#slider_1');
var slider.2 = document.querySelector('#slider_2');
then I'd be able to better utilize the ID already getting passed into my func's and eliminate tons of duplication.
I was hoping to simplify my funcs with something like a single call for slider.id.x.baseVal.value = x/scale; rather than having to have that code in each of the IF/ELSE conditions.
When I try that though, I get an error saying " Uncaught SyntaxError: Unexpected number ".
How should this be done?
You can't use a plain numeric key in an object.
You can do this, though:
var slider = {}; // or = [], if array syntax is more appropriate
slider[1] = ...
slider[2] = ...
Furthermore, the syntax you suggested isn't allowed if the key is actually a variable rather than a literal token.
In your example slider.id actually refers to the object with literal key id, not whatever value the variable id happens to have.
You have to put the variable inside square brackets, i.e. slider[id], so your function would be written thus:
function updateFromInput(id){
var x = +input[id].value;
x = Math.round((x*ratio)-offset);
slider[id].x.baseVal.value = x/scale;
};
You can't. The . is an invalid character for a variable identifier.
You can use it in object properties though.
var sliders = {
"slider.1": document.querySelector('#slider_1'),
"slider.2": document.querySelector('#slider_2')
};
Then use the square bracket version of the member operator to access the property.
alert( sliders["slider.1"].id );