Magento 2 – Changing Knockout a href Data-Bind to Link to Image

For Magento to apply the bindings you need to add your Knockout JS using the UI Components like so:

Inside the PHTML Template file

Pay extra attention to example-scope as it needs to match the scope of the markup.

Component links to your JS file, and template links to your HTML (or PHTML) file that contains the data-binds (and scope).

<script type="text/x-magento-init">
{
    "*": {
        "Magento_Ui/js/core/app": {
            "components": {
                "example-scope": {
                    "component": "VENDOR_MODULE/js/name-of-your-js-file",
                    "template": "Magento_Checkout/summary/item/details"
                }
            }
        }
    }
}
</script>

<div data-bind="scope: 'example-scope'">
    <!-- ko template: getTemplate() --><!-- /ko -->
</div>

Inside your JS file

define(['jquery', 'ko'], function($, ko) {
    return function(config) {
        // YOUR SCRIPT HERE
    }
});

At first, add your variable to defaults object, and you will be able to set default value for field.

defaults: {
    bankImage : null
}

Define your variable as observable

/**
 * Initialize observable properties
 */
initObservable: function () {
    this._super()
        .observe('bankImage');

    return this;
},

And you need to define correct success handler with component context:

success: (function(result) {
    this.bankImage(result.image);
}).bind(this),