What is the difference between String.slice and String.substring?

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String.slice() and String.substring() are two methods in JavaScript used to extract a portion of a string. While they both serve a similar purpose, there are differences in how they work.

Here are the key differences between String.slice() and String.substring():

  1. Negative Start Index:

    • String.slice(start, end) allows negative values for the start and end parameters, which count from the end of the string.
    • String.substring(start, end) does not accept negative values for start and end.

  2. Out-of-Range Values:

    • If the start value is greater than the end value, String.slice() will return an empty string.
    • If the start value is greater than the end value in String.substring(), it will swap the values and return the substring.

  3. Default Behavior:

    • When both start and end parameters are omitted, String.slice() returns the entire string.
    • When both start and end parameters are omitted, String.substring() also returns the entire string.

Here's an example demonstrating these differences:

javascript
const str = "Hello, World!";

// Using String.slice()
console.log(str.slice(0, 5));       // Output: "Hello"
console.log(str.slice(7));          // Output: "World!"
console.log(str.slice(-6));         // Output: "World!"
console.log(str.slice(6, 6));       // Output: ""
console.log(str.slice(12, 5));      // Output: ""

// Using String.substring()
console.log(str.substring(0, 5));   // Output: "Hello"
console.log(str.substring(7));      // Output: "World!"
console.log(str.substring(-6));     // Output: "Hello"
console.log(str.substring(6, 6));   // Output: ""
console.log(str.substring(12, 5));  // Output: "World!"

In this example, you can see that String.slice() and String.substring() behave differently when it comes to negative indices and out-of-range values. Understanding these differences can help you choose the appropriate method for your string manipulation needs.

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