How do I use .split() to break up a string into much smaller strings?
Question
I am making a code that is supposed to split up the alphabet into each letter on a different line. When I press the submit button, instead of displaying the letters, it does absolutely nothing at all. I am not sure why it is not working.
The output should be:
A:
B:
C:
D:
etc...
Any help is appreciated, but please do not use JQuery.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns:hi="http://www.w3.org/1999/xhtml"> <head> <title>My String Prototype</title> </head> <body> <form action = "#"> <input type="submit" id = "sub" value="Submit" onclick = "show_alphabet();"/> </form> <script type="text/javascript"> function show_alphabet () { var str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; str.prototype.sendArray= function (){ str.split(""); }; var arr = str.sendArray(); for (var i=0;i>arr.length;i++){ document.writeln(arr+":"); } } </script> </body> </html>
THANKS!
4 answers
solution1
2 2015-08-25 00:34:17
There's no need to split the string into characters if you can already do that by default:
var string = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'; for(var i = 0; i < string.length; i++){ document.getElementById('results').innerHTML += '\\n' + string[i]; }
<pre id="results"></pre>
solution2
1 2015-08-25 00:26:02
A few issues:
- Need to use
String.prototype.sendArray = - Need to
returna value - The
i > arr.lengthwill never be true - Need to use
arr[i]to access the current element.arris the entire array
This appears to work as expected:
function show_alphabet () {
var str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
String.prototype.sendArray = function (){
return str.split("");
};
var arr = str.sendArray();
for (var i = 0; i < arr.length; i++){
document.write(arr[i] + ":");
}
}
solution3
0 2015-08-25 00:23:30
There are these issues in your code:
- Your
sendArray()method needs to return its result. - You need to use
String.prototype.sendArray = function() {...}, notstr.prototype.sendArray = .... - When you create a new method on the prototype, you refer to the current instance as
this, notstr. - You have to reference the array item with
arr[i]. - Your comparison operation in your
forstatement is backwards.
I don't see why you're creating a new method that does nothing more than .split() , but if you want to do that, then you need to return the new value and use this instead of str and use String.prototype :
String.prototype.sendArray= function (){
return this.split("");
};
But, you don't really need that new method at all. Here's a working snippet with those above items fixed/changed:
function show_alphabet () { var str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; var arr = str.split(""); for (var i=0;i < arr.length;i++){ document.write(arr[i] + "<br>"); console.log(arr[i]); } } show_alphabet();
Or, using your sendArray() method:
String.prototype.sendArray= function (){ return this.split(""); }; function show_alphabet () { var str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; var arr = str.sendArray(); for (var i=0;i < arr.length;i++){ document.write(arr[i] + "<br>"); console.log(arr[i]); } } show_alphabet();
Prototype Usage Explanation
Here's a bit of explanation about the .prototype issue. The .prototype property is a direct property of a constructor function, not an individual object. That means it's a property of String , not str . Once you change it on String , then all objects created from that constructor will automatically inherit that change. So, when you add something to String.prototype , it will automatically be available on str as a direct method.
Then, when that method is invoked, the value of this will point to the current object so to reference a method or property on the current object from a prototyped method, you use this as the base. So, in this case, you would call this.split("") so split the current string.
solution4
0 ACCPTED 2015-08-25 00:28:29
Since this looks like homework, you don't get the answer outright.
1) When you split a string, you pick which character to split on. Ex: Splitting ("AB") (A then space then B). Returns an array with 2 elements. A & B.
2) You don't need all the string prototype stuff like you see in online help. var arr = str.split(... works fine.
3) Your greater than sign should be less than in for loop. You wnat to repeat while i is less than the length, not greater.
4) You don't want to writeln arr. You want to writeln arr[i], or the i'th element of the array.
5) To do the newline in HTML replace ":" with " <br /> "
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