Main functions applicable in Javascript variables

The built-in functions in JavaScript are common methods that can be applied in a general way to variables. These functions can be differentiated in whether they apply to variables of numeric or string type:

• Predefined functions for numeric type variables:
  • typeof: indicates the content type of a variable
    letnum = 10;
console.log(typeofnum);
  • isNaN: indicates if a variable is not a number
    letnum = 'hello';
console.log(isNaN(num));
    It will give us true as a result since the value of num is not a number
  • toString: Converts a value from a number to a text or string type.
    let number = 5;
console.log(typeofnumber);
console.log(typeof number.toString());
    The second result will give us that it is of type string having converted it.
  • toFixed(): Round a number to the given value.
    let number = 5.5;
console.log(number.toFixed());
    In this case, round without decimals.
    Result: 6

let number = 5.5;
console.log(number.toFixed(3));
In this case round to 3 decimals
Result: 5,500

• Predefined functions for variables of type string:
  • typeof. Indicates the content type of the variable.
    Example: typeof name_var
  • length. Measures the number of characters in a string.
    Example: name_var.length
  • includes. Checks that a specific text is included in a variable.
    Example: name_var.includes('text_to_search')
  • slice. Returns part of a string indicating the initial and final character number, counting the initial character from 0.
    Example: name_var.slices(2,5)
  • replace. Replaces one text with another within a variable.
    Example: name_var.replace('ub', 'jscr') →replace jscr with ub
  • trim. Remove leading and trailing whitespace within a variable.
    Example: name_var.trim()
  • split. Splits a text string into parts starting at a specified character.
    Example: name_var.split(',')→Splits the name_var string into multiple parts using the comma as a reference.

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