Function getNumberValueOfStyle

src/utils/dom.ts:9–21

(
  elem: HTMLElement,
  attr: keyof CSSStyleDeclaration
)

 * @param attr  CSS 属性
 */
export function getNumberValueOfStyle(
  elem: HTMLElement,
  attr: keyof CSSStyleDeclaration
): number | void {
  const value = window.getComputedStyle(elem)[attr]
  if (isString(value)) {
    // 匹配字符串的数字字符
    const numberValue = (value as string).match(/\d+/)
    if (numberValue) {
      return pInt(numberValue[0])
    }
  }
}

/**
 * 获取 DOM 元素距离页面的 top、left 值