Valid number

2023-11-17by@tim&@ChatGPT.Model: gpt-4

A valid number can be split up into these components (in order):

A decimal number or an integer.
(Optional) An 'e' or 'E', followed by an integer.
A decimal number can be split up into these components (in order):

(Optional) A sign character (either '+' or '-').
One of the following formats:
One or more digits, followed by a dot '.'.
One or more digits, followed by a dot '.', followed by one or more digits.
A dot '.', followed by one or more digits.
An integer can be split up into these components (in order):

(Optional) A sign character (either '+' or '-').
One or more digits.
For example, all the following are valid numbers: ["2", "0089", "-0.1", "+3.14", "4.", "-.9", "2e10", "-90E3", "3e+7", "+6e-1", "53.5e93", "-123.456e789"], while the following are not valid numbers: ["abc", "1a", "1e", "e3", "99e2.5", "--6", "-+3", "95a54e53"].

Given a string s, return true if s is a valid number.

Example 1:

Input: s = "0"
Output: true
Example 2:

Input: s = "e"
Output: false
Example 3:

Input: s = "."
Output: false

Constraints:

1 <= s.length <= 20
s consists of only English letters (both uppercase and lowercase), digits (0-9), plus '+', minus '-', or dot '.'.

Complete the following js function for me

/**
 * @param {string} s
 * @return {boolean}
 */
var isNumber = function(s) {
    
};

You can use the built-in JavaScript function isNaN() to check if a string is a valid number. However, this function returns true for the strings which contain 'e' or 'E' followed by a number. To handle this, you can split the string by 'e' or 'E' and check the length of the resulting array. If the length is more than 2, then return false because a valid number can contain at most one 'e' or 'E'. If the length is 1 or 2, then check if each part is a valid number.

Here is the JavaScript function:

/**
 * @param {string} s
 * @return {boolean}
 */
var isNumber = function(s) {
    let parts = s.split(/[eE]/);
    if (parts.length > 2) return false;
    for (let part of parts) {
        if (part === "" || isNaN(part)) return false;
    }
    return true;
};

This function works by first splitting the string by 'e' or 'E'. It then checks if each part is a valid number by using the isNaN() function. If any part is not a valid number, it returns false. Otherwise, it returns true.

tim

There is an error in this situation:
Input
s =
"Infinity"

Output
true
Expected
false

I apologize for that mistake. The previous implementation only checks if the string can be parsed to a number, it doesn't verify if the string matches the exact format described in the problem.

We will have to use a Regular Expression to validate the format. Here is the corrected function:

/**
 * @param {string} s
 * @return {boolean}
 */
var isNumber = function(s) {
    var reg = /^[+-]?(\.\d+|\d+\.?\d*)([eE][+-]?\d+)?$/;
    return reg.test(s);
};

This Regular Expression checks for the formats described in the problem:

A decimal number or integer
Optional 'e' or 'E' followed by an integer
Decimal with optional '+' or '-' sign, one or more digits followed by '.' and optional digits or '.' followed by one or more digits.
Integer with optional '+' or '-' sign and one or more digits.

If the string matches this format, reg.test(s) will return true else false.

OpenPrompt