JavaScript - How to get at specific value in a string? - Stack Overflow

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I have a string from which I am trying to get a specif value. The value is buried in the middle of the string. For example, the string looks like this:

 Content1Save

The value I want to extract is "1";

Currently, I use the built-in substring function to get to remove the left part of the string, like this:

MyString = "Content1Save";
Position = MyString;
Position = Position.substring(7);
alert(Position); // alerts "1Save"

I need to get rid of the "Save" part and be left with the 1;

How do I do that?

+++++++++++++++++++++++++++++++++++++++++ ANSWER

Position = Position.substr(7, 1);

QUESTION

What's the difference between these two?

Position = Position.substr(7, 1);
Position = Position.substring(7, 1);

I have a string from which I am trying to get a specif value. The value is buried in the middle of the string. For example, the string looks like this:

 Content1Save

The value I want to extract is "1";

Currently, I use the built-in substring function to get to remove the left part of the string, like this:

MyString = "Content1Save";
Position = MyString;
Position = Position.substring(7);
alert(Position); // alerts "1Save"

I need to get rid of the "Save" part and be left with the 1;

How do I do that?

+++++++++++++++++++++++++++++++++++++++++ ANSWER

Position = Position.substr(7, 1);

QUESTION

What's the difference between these two?

Position = Position.substr(7, 1);
Position = Position.substring(7, 1);

• javascript

Share Improve this question Follow edited Aug 16, 2011 at 17:28 Evik James asked Aug 16, 2011 at 17:06 Evik JamesEvik James 10.5k1919 gold badges7676 silver badges123123 bronze badges 4

• 1 Do you KNOW that you will be saving a NUMBER from the middle of a string with nothing but LETTERS around it? – josh.trow Commented Aug 16, 2011 at 17:08
• 1 Do the strings follow any general pattern? – Felix Kling Commented Aug 16, 2011 at 17:08
• The number in the string will always be a 1, 2, 3, or 4. – Evik James Commented Aug 16, 2011 at 17:25
• Regarding your update, have a look at developer.mozilla/en/JavaScript/Reference/Global_Objects/… and developer.mozilla/en/JavaScript/Reference/Global_Objects/… – Felix Kling Commented Aug 16, 2011 at 17:35

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4 Answers 4

Sorted by: Reset to default 4

You can use the substr^[MDN] method. The following example gets the 1 character long substring starting at index 7.

Position = Position.substr(7, 1);

Or, you can use a regex.

Position = /\d+/.exec(Position)[0];

I would suggest looking into regex, and groups.

Regex is built essentially exactly for this purpose and is built in to javascript. Regex for something like Content1Save would look like this:

rg = /^[A-Za-z]*([0-9]+)[A-Za-z]*$/

Then you can extract the group using:

match = rg.exec('Content1Save');
alert(match[1]);

More on regex can be found here: http://en.wikipedia/wiki/Regular_expression

It highly depends on the rules you have for that middle part. If it's just a character, you can use Position = Position.substring(0, 1). If you're trying to get the number, as long as you have removed the letters before it, you can use parseInt.

alert(parseInt("123abc")); //123
alert(parseInt("foo123bar")); //NaN

If you're actually trying to search, you'll more often than not need to use something called Regular Expressions. They're the best search syntax JavaScript avails.

var matches = Position.match(/\d+/)
alert(matches[0])

Otherwise you can use a series of substr's, but that implies you know what is in the string to begin with:

MyString.substr(MyString.indexOf(1), 1);

But that is a tad annoying.

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