Checks if a bot is auto-clicking a specified DOM element.

clickBotChecker.js

/**
 * clickBotChecker.js
 * ------------------------------------------------------------------------------
 * ABOUT:
 *      clickBotChecker.userIsBot() returns true if it thinks a bot is clicking your specified DOM element.
 * METHOD
 *      .userIsBot() does the following to determine auto-clicking behavior:
 *          1. Store the timestamp of every n clicks for analysis
 *          2. Once three timestamps have been stored, every n clicks, find the absolute value of the difference between:
 *              a. ( (the average of the last three timestamps) * 3 )
 *              b. ( the last three timestamps * 3 )
 *          3. If the absolute value of the difference between the two values is less than 5,
 *              then the user is clicking with extremely precise frequency and is most likely a bot.
 * USAGE:
 *      1. Put this code above where you want it to be used.
 *      2. Inside your click event handler, increment clickBotChecker.currentSessionScore by 1.
 *      3. Use clickBotChecker.userIsBot() inside your DOM element click event handler and handle the result (true / false).
 **/

const clickBotChecker = {
    
    /* global app variables **/
    currentSessionScore: 0,
    timeSinceLastCheck: Date.now(),
    timeGapsBetweenChecks: [],
    
    userIsBot: (checkFrequency) => {

        /** do a click frequency check every checkFrequency clicks. **/
        if ( ( clickBotChecker.currentSessionScore > checkFrequency * 2 ) &&
            ( clickBotChecker.currentSessionScore % checkFrequency === 0 ) ) {

            /* log click behavior */
            const now = Date.now()
            const timeGap = now - clickBotChecker.timeSinceLastCheck
            clickBotChecker.timeSinceLastCheck = now
            clickBotChecker.timeGapsBetweenChecks.push( timeGap )

            /* determine if click behavior implies bot usage */
            if (clickBotChecker.timeGapsBetweenChecks.length > 3) {
                const gapsToCheck = clickBotChecker.timeGapsBetweenChecks.slice( -3 )
                const averageOfLastThreeChecks = (
                    parseInt( gapsToCheck.reduce( ( n, m ) => n + m, 0 ) / gapsToCheck.length)
                )
                const userIsBot = ( Math.abs( gapsToCheck[0] - averageOfLastThreeChecks ) < 5 ) &&
                    ( Math.abs( gapsToCheck[1] - averageOfLastThreeChecks ) < 5 ) &&
                    ( Math.abs( gapsToCheck[2] - averageOfLastThreeChecks ) < 5 )

                return userIsBot
            }
        }
    },
}