//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-1indexOf();//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-1lastIndexOf();//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();