Screen Capture a single webElement, not the whole page in JavaScript, Selenium

capture.js

const webdriver = require('selenium-webdriver'),
    By = webdriver.By,
    until = webdriver.until;
const fs = require("fs");

function takeScreenshot(driver, webElement, imagePath) { // driver -> webDriver; webElement -> WebElement; imagePath -> physical path to save the image 
    var base64Data = "";
    var location = {};
    var bulk = [];
    driver.then(_ => {
        webElement.getLocation().then(e => {
            location.x = e.x;
            location.y = e.y;
        });
        webElement.getSize().then(e => {
            location.height = e.height;
            location.width = e.width;
        });
        driver.manage().window().getSize().then(e => {
            location.browserHeight = e.height;
            location.broserWidth = e.width;
        });
    }).then(_ => {
        driver.takeScreenshot().then(data => {
            base64Data = data.replace(/^data:image\/png;base64,/, "");
        });
    }).then(_ => {
        const sizeLimit = 700000; // around 700kb
        const imgSize = base64Data.length;
        driver.executeScript(() => {
            window.temp = new Array;
        }).then(_ => {
            for (var i = 0; i < imgSize; i += sizeLimit) {
                bulk.push(base64Data.substring(i, i + sizeLimit));
            }
            bulk.forEach((element, index) => {
                driver.executeScript(() => {
                    window.temp[arguments[0]] = arguments[1];
                }, index, element);
            });
        });
    }).then(_ => {
        driver.executeScript(() => {
            var tempBase64 = window.temp.join("");
            var image = new Image();
            var location = arguments[0];
            image.src = "data:image/png;base64," + tempBase64;
            image.onload = function () {
                var canvas = document.createElement("canvas");
                canvas.height = location.height;
                canvas.width = location.width;
                canvas.style.height = location.height + 'px';
                canvas.style.width  = location.width + 'px';
                var ctx = canvas.getContext('2d');
                ctx.drawImage(image, -location.x, -location.y);
                window.canvasData = canvas.toDataURL();
                window.temp = [];
            }
        }, location);
    }).then(_ => {
        return driver.executeScript(() => {
            var data = window.canvasData;
            window.canvasData = "";
            return data;
        }).then(data => {
            var tempData = data.replace(/^data:image\/png;base64,/, "");
            fs.writeFileSync(imagePath, tempData, "base64");
            console.log("Image capture complete");
        });
    });
}