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