最后，我找到了如何更改非帧$button_labels 的WP_Customize_Image_Control 通过扩展其类，而不是重新分配新$type 并实施enqueue() 函数将纯JavaScript代码排队，以操作非框架标签，如下面所示，更改动态\'default\' 标签依据.addEventListener("click", handler) 其动态.button:

class WP_Customize_Custom_Control extends WP_Customize_Image_Control {

    public function enqueue() {
        // There\'s no parent::enqueue() function.
        ?>
<script>
    // Will execute if the specific element is ready, in pure JavaScript way.
    var elemReadyCheckInterval = setInterval(function() {
        if (document.getElementById("customize-control-custom")) {
            clearInterval(elemReadyCheckInterval);

            var controlCustom = document.getElementById("customize-control-custom");
            var controlButton = controlCustom.getElementsByClassName("button")[0];

            controlButton.addEventListener("click", function () {
                buttonClick(controlCustom, controlButton);
            });
        }
    }, 10);

    function buttonClick(custom, button) {
        var previousLabel = button.innerHTML;
        var buttonClickFunc = arguments.callee;

        var elemReadyCheckInterval = setInterval(function() {
            // Remove the EventListener `buttonClick(custom, button)` from the `button`.
            button.removeEventListener(\'click\', buttonClickFunc);

            // Assign the new element to the `button` because it\'s dynamically changing!
            button = custom.getElementsByClassName("button")[0];
            // Compare the `previousLabel` to the current `button` label.
            if (previousLabel !== button.innerHTML) {
                clearInterval(elemReadyCheckInterval);

                // If the dynamic label is \'Default\'.
                if (button.innerHTML === \'Default\')
                    button.innerHTML = \'Custom Default\';

                button.addEventListener("click", function () {
                    buttonClick(custom, button);
                });
            }
        }, 10);
    }
</script>
        <?php
    }

}

非框架不变$button_labels 这样做，就是一个bug！

$this->button_labels = array(
  \'select\'       => __( \'Custom Select Image\' ),
  \'change\'       => __( \'Custom Change Image\' ),
  \'remove\'       => __( \'Custom Remove\' ),
  \'default\'      => __( \'Custom Default\' ),
  \'placeholder\'  => __( \'Custom No image selected\' ),
);