//https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String
//返回对应索引的字符

chartAt()

//返回对应所引的字符的统一码(Unicode value)

charCodeAt()

//Returns a non-negative integer that is the UTF-16 encoded code point value at the given position.

codePointAt();

//拼接两个字符串，并返回一个新的字符串

concat();

//Determines whether one string may be found within another string.

includes();

//Determines whether a string ends with the characters of another string.

endsWidth();

//返回一个字符串在另一个字符串中首次出现的位置，如果查找不到，返回-1

indexOf();

//返回一个字符串在另一个字符串中末次出现的位置，如果查找不到，返回-1

lastIndexOf();

//Returns a number indicating whether a reference string comes before or after or is the same as the given string in sort order.

localeCompare();

//用字符串匹配一个字符串

mach();

//Returns the Unicode Normalization Form of the calling string value.

normalize();

//Returns a string consisting of the elements of the object repeated the given times.

repeat();

//找出字符串中和正则表达式匹配的部分，并用一个新的子串替换

replace();

//找出字符串中和正则表达式匹配的部分

search();

//截取字符串的一部分返回

slice();

//把一个字符串分割成数组，分割点为传入的子串

split();

//Returns the characters in a string beginning at the specified location through the specified number of characters.

substr();

//

substring();

//

toLocalLowerCase();

//

toLocalUpperCase();

toLowerCase();

toSource();

toString();

toUpperCase();

trim();

valueOf();