使用webpack时jQuery的选择器未定义

Question

I was learning webpack and had created a module to do a simple task: click an element to add this css property on it margin-right: 5rem;

import $ from 'jquery'

class ShiftRight {
    constructor() {
        this.more = $('.more')
        this.shifting()
    }

    shifting() {
        this.more.click(function() {
            this.more.addClass('more--clicked')
        })
    }
}

export default ShiftRight

HTML's part is simple too:

    <div class="more">
        <div class="more-sign"></div>
    </div>

The error message: Cannot read property 'addClass' of undefined . How come this.more is undefined? Is that because of jQuery? What's the pure JavaScript way to cooperate with webpack in this case?

Answer 1

jQuery seems to be loaded because you get an error on this.mode.addClass not on $(".mode") or this.more.click .

The problem is the context, inside the click callback function, this doesn't refer to the ShiftRight instance, it refers to the clicked element. Using $(this).addClass("more--clicked")

shifting() {
    this.more.click(function() {
        $(this).addClass('more--clicked')
    })
}

or an arrow function

shifting() {
    this.more.click(() => {
        this.more.addClass('more--clicked')
    })
}

should fix that

Answer 2

if it is a jquery problem try to add this to your webpack config

plugins: [
    new webpack.ProvidePlugin({
        $: "jquery",
        jQuery: "jquery"
    })
]