Modern JavaScript Part 05: Additional string methods

Sun Jun 03 2018 / book

Additional string methods

We are going to cover 4 new strings method:

  • startsWith()
  • endsWith()
  • includes()
  • repeat()

 

startsWith()

This new method will check if the string starts with the value we pass in:

    const code = "ABCDEFG";

    code.startsWith("ABB");
    // false
    code.startsWith("abc");
    // false, startsWith is case sensitive
    code.startsWith("ABC");
    // true

We can pass an additional parameter, which is the starting point where the method will begin checking.

    const code = "ABCDEFGHI"

    code.startsWith("DEF",3);
    // true, it will begin checking after 3 characters

 

endsWith()

Similarly to startsWith() this new method will check if the string ends with the value we pass in:

    const code = "ABCDEF";

    code.endsWith("DDD");
    // false
    code.endsWith("def");
    // false, endsWith is case sensitive
    code.endsWith("DEF");
    // true

We can pass an additional parameter, which is the number of digits we want to consider when checking the ending.

    const code = "ABCDEFGHI"

    code.endsWith("EF", 6);
    // true, 6 means that we consider only the first 6 values ABCDEF, and yes this string ends with EF therefore we get *true*

 

includes()

This method will check if our string includes the value we pass in.

    const code = "ABCDEF"

    code.includes("ABB");
    // false
    code.includes("abc");
    // false, includes is case sensitive
    code.includes("CDE");
    // true

 

repeat()

As the name suggests, this new method will repeat what we pass in.

    let hello = "Hi";
    console.log(hello.repeat(10));
    // "HiHiHiHiHiHiHiHiHiHi"