rendezvous with cassidoo #189 - Interview question of the week

validNumber.js

/**
 * From: https://buttondown.email/cassidoo/archive/success-is-more-a-function-of-consistent-common/
 * @param {string} str String
 * @returns {boolean} If the given string represents a valid number.
 * @example
 * $ validNumber("-123.456")
 * -> true
 * 
 * $ validNumber("abc123")
 * -> false
 */
function validNumber (str) {
    let isFloat = false
    
    for (let i = 0; i < str.length; i++) {
        const char = str[i]

        if (i === 0 && strIncludes("+-.", char))
            if (str.length < 2) return false
            else continue

        else if (char === ".")
            if (!isFloat) isFloat = true
            else return false

        else if (!strIncludes("0123456789", char)) return false
    }
    return true
}

/**
 * @param {string} dictionary
 * @param {string} character
 * @returns {boolean} If the `dictionary` contains the given `character`.
 * @example
 * $ validNumber("abc123", "b")
 * -> true
 * 
 * $ validNumber("def456", "g")
 * -> false
 */
function strIncludes (dictionary, character) {
    for (let item of dictionary)
        if (character === item) return true
    
    return false
}