Removing first k characters from string in JavaScript

We are required to write a JavaScript function that takes in a string and a number, say k and returns another string with first k characters removed from the string.

For example: If the original string is ?

const str = "this is a string"

and,

n = 4

then the output should be ?

const output = " is a string"

Method 1: Using substr() Method

The substr() method extracts characters from a string starting at a specified position.

const str = 'this is a string';

const removeN = (str, num) => {
    const { length } = str;
    if(num > length){
        return str;
    };
    const newStr = str.substr(num, length - num);
    return newStr;
};

console.log(removeN(str, 3));
console.log(removeN(str, 4));
console.log(removeN(str, 10));

s is a string
 is a string
tring

Method 2: Using slice() Method (Recommended)

The slice() method is the modern and preferred approach for extracting parts of a string.

const removeFirstK = (str, k) => {
    if (k >= str.length) {
        return "";
    }
    return str.slice(k);
};

const originalString = "JavaScript Programming";
console.log("Original:", originalString);
console.log("Remove first 4:", removeFirstK(originalString, 4));
console.log("Remove first 10:", removeFirstK(originalString, 10));
console.log("Remove first 25:", removeFirstK(originalString, 25));

Original: JavaScript Programming
Remove first 4: Script Programming
Remove first 10:  Programming
Remove first 25: 

Method 3: Using substring() Method

The substring() method returns characters between two indices in a string.

const removeKChars = (str, k) => {
    return str.substring(k);
};

const text = "Hello World";
console.log("Original:", text);
console.log("Remove first 6:", removeKChars(text, 6));
console.log("Remove first 2:", removeKChars(text, 2));

Original: Hello World
Remove first 6: World
Remove first 2: llo World

Comparison of Methods

Edge Cases

Here's how different methods handle edge cases:

const testString = "Test";

// When k is greater than string length
console.log("slice(10):", testString.slice(10));        // ""
console.log("substring(10):", testString.substring(10)); // ""

// When k is 0
console.log("slice(0):", testString.slice(0));          // "Test"
console.log("substring(0):", testString.substring(0));   // "Test"

// When k equals string length
console.log("slice(4):", testString.slice(4));          // ""
console.log("substring(4):", testString.substring(4));   // ""

slice(10): 
substring(10): 
slice(0): Test
substring(0): Test
slice(4): 
substring(4): 

Conclusion

Use slice() as the preferred method for removing first k characters from strings. Avoid substr() as it's deprecated, and consider substring() for basic use cases.