【lodash源碼】_.startsWith()

函數檢查字符串是否是目標字符開始的
/**
 * Checks if `string` starts with the given target string.
 */

function startsWith(string, target, position) {
  const { length } = string
  position = position == null ? 0 : position
  if (position < 0) {
    position = 0
  }
  else if (position > length) {
    position = length
  }
  target = `${target}` // es6中模板字符`xxxxx`,在字符串中嵌入變量，例如：`xx${變量}xx`
  return string.slice(position, position + target.length) == target
}
export default startsWith

測試： _.startsWith('abc', 'ab')=>/true