Why two different methods slice() & substring()?

Question

var name="nameSomnath";//remove name

I can do with slice()

var result = name.slice( 4 );

Same can be done with substring()

var result = name.substring( 4 );

So what makes them different. I have seen the link Here which elaborates the difference .But we can do the same thing by using any one method ie slice() or substring().So why there was need to have two methods.

Answer 1

Even though it looks superficially like slice and substring do the same thing, the big difference is in how they handle negative arguments.

When JavaScript was first created in Netscape 2.0, there was just a substring method. If either of its arguments are negative, they are treated as 0.

When JavaScript 1.2 was introduced with Netscape 4.0, they wanted to add the behavior of allowing negative indexes to mean distances from the end of the string. They couldn't change substring to have this new behavior because it would break backward compatibility with scripts that expected negative indexes to be treated as 0, so they had to create a new function to support the added feature. This function was called slice, and was implemented on Array as well as String.

Another, smaller difference is that with substring the order of the arguments doesn't matter, so substring(1, 4) is the same as substring(4, 1). With slice, order does matter, so slice(4, 1) will just yield an empty string.

Answer 2

One item that makes them different is the second parameter that you have omitted

• slice: the second parameter is the end index (exclusive) of the range to take.
• substr: the second parameter is the length of the string to take from the index specified with the first parameter

Can you completely replicate the behavior of one method with the other on string instances? Yes. Why they chose to include both is probably lost to history. My guess though would be familiarity. I bet there are very few frameworks out there which have slice for strings but plenty that have substr.