Simple log-library, Node-4 friendly

logger.js

 /*
Logging module
*/

'use strict'

const Logger = function(options) {
    this.init(options)
}

const p = Logger.prototype

const defaultLevel = 'info'
const levels = ['debug', 'info', 'warn', 'error']

p.init = function(options) {
    this.logLevel = (options && options.logLevel) || defaultLevel
}

p.shouldLog = function(level) {
    return (levels.indexOf(level) >= levels.indexOf(this.logLevel))
}

p.stringify = function(messages) {
    const stringified = []

    // eslint-disable-next-line no-plusplus
    for (let i = 0; i < messages.length; i++) {
        let message = messages[i]
        if (typeof message !== 'string') {
            message = JSON.stringify(message)
        }
        stringified.push(message)
    }

    return stringified
}

p.log = function(level) {
    if (!this.shouldLog(level)) return

    const messages = this.stringify([].slice.call(arguments).slice(1))
    // eslint-disable-next-line no-plusplus
    for (let i = 0; i < messages.length; i++) {
        const count = (messages.length > 1) ? `:${i}` : ''
        // eslint-disable-next-line no-console
        console.log(`${level}${count}: ${messages[i]}`)
    }
}

p.debug = function() {
    // eslint-disable-next-line prefer-rest-params
    const args = ['debug'].concat([].slice.call(arguments))
    // eslint-disable-next-line prefer-spread
    this.log.apply(this, args)
}

p.info = function() {
    // eslint-disable-next-line prefer-rest-params
    const args = ['info'].concat([].slice.call(arguments))
    // eslint-disable-next-line prefer-spread
    this.log.apply(this, args)
}

p.warn = function() {
    // eslint-disable-next-line prefer-rest-params
    const args = ['warn'].concat([].slice.call(arguments))
    // eslint-disable-next-line prefer-spread
    this.log.apply(this, args)
}

p.error = function() {
    // eslint-disable-next-line prefer-rest-params
    const args = ['error'].concat([].slice.call(arguments))
    // eslint-disable-next-line prefer-spread
    this.log.apply(this, args)
}

module.exports = Logger