This tool lib allows to make strings checks and modification. It's useful for preparing requests for API calls to sanitize (str_mod) or validate (str_check) fields.

str_mod.js

// Example usage

// Case 1
// const last6 = str_mod(trim(), last(6));
// console.log(last6("  test string  ")); // returns "string"

// Case 2
// console.log(str_mod("  test string  ", trim(), last(6))); // returns "string"

const trim = () => {
    return (str) => str.trim();
};

const last = (n) => {
    return (str) => str.slice(-n);
};

const first = (n) => {
    return (str) => str.slice(0, n);
};

const defaultVal = (defaultValue) => {
    return (str) => (str ? str : defaultValue);
};

const exclude = (regexp) => {
    return (str) => str.replace(new RegExp(regexp, 'g'), '');
};

const alphanum = () => {
    return (str) => str.replace(/[^a-zA-Z0-9]/g, '');
};

const num = () => {
    return (str) => str.replace(/[^0-9]/g, '');
};

const inList = (arr) => {
    return (str) => (arr.includes(str) ? str : null);
};

const min = (n) => {
    return (str) => (str.length < n ? null : str);
};

const max = (n) => {
    return (str) => (str.length > n ? null : str);
};

const length = (n) => {
    return (str) => str.length === n ? str : null;
}

const join = (arr, separator = ', ') => {
    return () => arr.filter(item => item).join(separator);
};

const firstNonEmpty = (arr) => {
    return () => {
        for (let item of arr) {
            if (item) return item;
        }
        return null;
    };
};

const getLastPart = (separator = ':') => {
    return (str) => {
        const parts = str.split(separator);
        return parts[parts.length - 1];
    };
};

const addTimeStamp = () => {
    return (str) => `${str}_${Date.now()}`;
};

const toInt = () => {
    return (str) => {
        const match = str.match(/^(\d+)$/);
        return match ? parseInt(match[0], 10) : null;
    };
};

const toNumber = () => {
    return (str) => {
        const match = str.match(/^[-+]?\d*\.?\d+(?:[eE][-+]?\d+)?$/);
        return match ? parseFloat(match[0]) : null;
    };
};

// Define the str_mod function
const str_mod = (strOrFunc, ...funcs) => {
    // trim string on start and end of processing
    funcs.shift(trim());
    funcs.push(trim());

    const applyFuncs = (str, funcs) => {
        return funcs.reduce((acc, func) => acc == null ? null : func(acc), str);
    };

    if (typeof strOrFunc === 'string') {
        // If the first argument is a string, apply all funcs to the string
        return applyFuncs(strOrFunc, funcs);
    } else {
        // Otherwise, return a function that takes a string and applies all funcs
        return (str) => applyFuncs(str, [strOrFunc, ...funcs]);
    }
};

const str_check = (strOrFunc, ...funcs) => {
    if (typeof strOrFunc === 'string') {
        // If the first argument is a string, apply all funcs to the string
        const initialStr = strOrFunc.trim();
        const finalStr = str_mod(strOrFunc, ...funcs);
        return initialStr === finalStr ? finalStr : null;
    } else {
        // Otherwise, return a function that takes a string and applies all funcs
        return (str) => {
            // applyFuncs(str, [strOrFunc, ...funcs]);
            const initialStr = str.trim();
            const finalStr = str_mod(str, strOrFunc, ...funcs);
            return initialStr === finalStr ? finalStr : null;
        }
    }
};

module.exports = {
    str_mod,
    str_check,
    trim,
    last,
    first,
    defaultVal,
    exclude,
    alphanum,
    num,
    inList,
    min,
    max,
    length,
    join,
    firstNonEmpty,
    getLastPart,
    addTimeStamp,
    toInt,
    toNumber
};