String

Some of the basic string methods you must familiar with in your programming languages.

• Position, Index, Search

  • Beginning of character.

  • String replace without regular expression.

  • For example :

    var fruitString = "Apple, Banana,Orange";
    if (fruitString.indexOf("Apple") > 0) {
    console.log("Apple is here");
    }

    or

    ```

    var fruitString = "Apple, Banana,Orange";

    if (fruitString.indexOf("Apple") != -1) {

    console.log("Apple is here");

    }

• Comparison

  • equal

  • In general, that is ==.

  • object comparison, In java, use like

    a.equals(b)

• Length

  • Declaration blank or null :

    Be careful to declare a string.

    In C, string is immutable.

    But in the modern languages, java, js, python, go, string can be changed.

  • Is String empty? How to check if string is empty? Use length, but just need to make sure not null first.

    if (str != null && str.length > 0) {
    
    }

• Token Parser

  • Repetitive pattern match

  • Parse to array

  • For example: parse the following string to array:

    var fruitString = "Apple, Banana,Orange";
    var fruits = fruitString.split(",");

• Convert

  • String to Number

  • In the web page data submission, those data are just string. Any particular ID need to convert to integer or long.

  • For example :

    var a = "123";
    var i = parseInt(a, 10);

    a = "123"
    i = int(a)

• Join string

  • Join string array in a string.

  • It's considering to be better performance than string appending.

  • For example :

    ```

    var fruits = ["Apple", "Banana", "Orange"];

    var fruitString = fruits.join(", ");

  * String appending is not the best practice.

  var fruits = ["Apple", "Banana", "Orange"]; var fruitString = ""; furitString += fruits[0] + ", "; furitString += fruits[1] + ", "; furitString += fruits[2] + ", ";

  ```

• Remove extra spacing

  • Remove leading spacing.

  • Remove trailing spacing".

  • For example :

    ```

    var name = " John Doe ";

    name = name.trim();

  ```

• To uppercase, lowercase.

  • Most use in case insensitive search pattern match and case insensitive search order.

• Regular Expression

  • For pattern match.

  • String replacement.

  • For example : remove line break.

    • Online regular expression match

    • Look around extension (lookahead, lookbehind)