CODEWITHSUNDEEP
javascript
Alan2
Alan2

Reputation: 24572

Can I chain a substring check in javascript?

I am using the following code:

if (store.getItem('TopicID') != "00")

TopidID is always 4 digits and what I need to do is change this to check if the last two digits are "00".

Can I do this as part of the above by just adding ".substring(from, to)" or do I need to put this into a variable and then check the variable?

Upvotes: 0

Views: 808

Answers (7)

KooiInc
KooiInc

Reputation: 122956

Use if (!/00$/.test(store.getItem('TopicID')) to check for the last 2 digits not forming '00'. That way the length of the value of store.getItem('TopicID') doesn't matter, you always check for the last two characters of the value, and you don't need the substring 'chaining'.

By the way, I supposed store.getItem('TopicID') returns a String here.

To be complete and in response to Paul Phillips comment: in !/00$/.test([somestring]), /00$/ is a Regular Expression, a special text string for describing a search pattern. In this case it means: for the string resulting from store.getItem('TopicID'), check if you can find 2 consecutive zero's, where the $-sign means 'check for that pattern at the end of the string'.

To be even more complete on the subject of 'chaining': as long as a method is contained by the object to chain, everything can be chained. A completely nonsensical example of that:

Number(/00$/.test('0231')) //convert a boolean to a Number
 .toFixed(2)               //a Number has the toFixed method
 .split('.')[1]            //toFixed returns a String, which has method split
 .substr(1)                //the second element is a string, so substr applies
 .concat(' world')         //still a string, so concat will do
 .split(' ')               //string, so split works
 .join(' hello ')          //from split an array emerged, so join applies
;
//=> result of this chain: '0 hello world'

Upvotes: 1

Someth Victory
Someth Victory

Reputation: 4549

 var yourString = (store.getItem('TopicID'))
 if(yourString.substring((yourString.length - 2), 2) == "00")

The code above doesn't care how long your string is. It gets the last two digits and compare to "00"

Upvotes: 0

Florian Margaine
Florian Margaine

Reputation: 60787

Can I do this as part of the above by just adding ".substring(from, to)"

Yes, you can. You got the wrong syntax, though.

if (store.getItem('TopicID').substring( 2 ) != "00")

Upvotes: 0

panda-34
panda-34

Reputation: 4209

if it's four digits, you can use

if (store.getItem('TopicID') % 100)

Upvotes: 0

Engineer
Engineer

Reputation: 48803

Try to use substr or substring with negative start:

if ( store.getItem('TopicID').substr(-2) !== "00" ){...}

or 

if ( store.getItem('TopicID').substring(-2) !== "00" ){...}

Upvotes: 0

Siva Charan
Siva Charan

Reputation: 18064

you can do using slice too

if (store.getItem('TopicID').slice(2,4) != "00") {
      // Do Your Stuff
}

Upvotes: 0

Paul Phillips
Paul Phillips

Reputation: 6259

Chaining it would work. So would extracting a local variable. So no, you don't need to. Do it if you think it makes the code more readable.

Upvotes: 0

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