Can someone please explain to me what does the -1 mean/represent in this if statement.

    if(window.location.href.indexOf("pathname") != -1) {
    //do something
     };

The way I think would be to do something like (if true then do something)

   if(window.location.href.indexOf("pathname") == 0) {
    //do something
     };

0 being 1? That means it's always false unless 'pathname' exists which bees true?

This confuses me all the time. Should I use != -1, == 0 or >=0.

Can someone please explain to me what does the -1 mean/represent in this if statement.

    if(window.location.href.indexOf("pathname") != -1) {
    //do something
     };

The way I think would be to do something like (if true then do something)

   if(window.location.href.indexOf("pathname") == 0) {
    //do something
     };

0 being 1? That means it's always false unless 'pathname' exists which bees true?

This confuses me all the time. Should I use != -1, == 0 or >=0.

• javascript

• 1 First of all, have you find out how the indexOf() method works? Please go through some tutorial on it before asking question. – gjman2 Commented Jul 15, 2013 at 2:24

9 Answers 9

indexOf is a function that locates the index (position) of an object in any other given object whether it be a char in a string, or a byte in a buffer... etc.

If it is not found, just for safety purposes it returns -1. This is because 0 is an index in the object.

For example:

"hello world"

h = 0
e = 1
l = 2
...

so if it is not found it will be -1, and if it is found it will be >= (greater than or equal to) 0. so essentially != -1 and >= 0 will return the same output.

Based on the docs, indexOf returns -1 if it doesn't find a match of the string in your argument. Otherwise, it returns the index of your string.

Quote from docs:

Returns the first index at which a given element can be found in the array, or -1 if it is not present.

-1 is used to indicate that there wasn't a match when searching for the substring you provided. All output > -1 indicates the start position of where the substring was found in the larger string

Read more here: http://www.w3schools./jsref/jsref_indexof.asp

indexOf returns the index at which the substring begins in your string, not a true/false depending on the presence of the substring in your string.

Strings and arrays are zero-indexed in JavaScript, so a return value of 0 means that the substring begins at the very beginning of your string. -1 isn't a valid index, which is why indexOf returns it when the string wasn't found.

indexOf returns -1 when the parameter string is not found. It also returns >=0 if it's found. So if you are checking whether the string occurs or not, !=-1 and >=0 is same thing. It returns 0 if match starts from the first index.

.indexOf() is meant to look for a match - in your case of substring. If the function finds a match it returns the index in which it starts. If no match was found it returns -1. You can read the docs here.

As per your question:

if(window.location.href.indexOf("pathname") == 0) {
    // code here will be executed only if your current URL
    // starts with 'pathname' (0 is the first index in a String)
};

if(window.location.href.indexOf("pathname") != -1) {
    // code here will be executed only if your current URL
    // contains the string 'pathname' (-1 means no match was found)
};

-1 -- no such a string inside

0 -- the searchable string is in the very beginning (its first symbol is the 0's symbol in the subject string)

http://www.w3schools./jsref/jsref_indexof.asp

The indexOf() method returns the position of the first occurrence of a specified value in a string.

So use >=0 to check if substring is in the string and ==-1 to check that substring is absence

Check this link http://www.w3schools./jsref/jsref_indexof.asp

Please go through some tutorial and find out about the indexOf(). Btw, indexOf() is javascript not jQuery :)