以Vue + Element Dialog为例，用ResizeObserver监听容器高度变化，当高度大于最大高度（出现滚动条），右边距减去滚动条的宽度，反之恢复正常边距

<el-dialog><div class="dialog_body" v-fix-scroll-bar="this"><slot /></div>
</el-dialog>

export default {data() {return {resizeObserver: null,}},methods: {setScrollBar() {this.resizeObserver = new ResizeObserver((entries) => {for (let entry of entries) {const cr = entry.contentRect;const el_dialog_body = entry.target.parentNode;const maxHeight = window.getComputedStyle(el_dialog_body).maxHeight;if (maxHeight && cr.height > parseInt(maxHeight)) {el_dialog_body.style.paddingRight = "20px";} else {el_dialog_body.style.paddingRight = "32px";}}});},},mounted() {this.setScrollBar();},directives: {fixScrollBar: {inserted: (el, binding) => {const _this = binding.value;_this.resizeObserver.observe(el);},unbind: (el, binding) => {const _this = binding.value;_this.resizeObserver.unobserve(el);},},},
}