let str ='hello, how are you doing? username!'// 截取 ? 前面的字符串:let before1 = str.substring(0,str.lastIndexOf("?"))// 不包含 ?
console.log(before1,'before1---------------');// hello, how are you doing let before2 = str.substring(0,str.lastIndexOf("?")+1)// 包含 ?
console.log(before2,'before2---------------');// hello, how are you doing?// 截取 ? 后面的字符串:let after1 = str.substring(str.lastIndexOf("?")+1)// 不包含 ?
console.log(after1,'after1-----------------');// username!let after2 = str.substring(str.lastIndexOf("?"))// 包含 ?
console.log(after2,'after2-----------------');// ? username!
多个相同符号截取:
let str ='hello? how are you doing? username!'// 截取第一个 ? 前面的字符串let index1 = str.indexOf("?")let string1 = str.substring(0, index1);// 不包含 ?
console.log(string1,'string1------')// hellolet string11 = str.substring(0, index1 +1);// 包含 ?
console.log(string11,'string11------')// hello?// 截取第一个 ? 后面的字符串let index2 = str.indexOf("?")let string2 = str.substring(index2 +1, str.length);// 不包含 ?
console.log(string2,'string2------')// how are you doing? username!let string22 = str.substring(index2, str.length);// 包含 ?
console.log(string22,'string22------')// ? how are you doing? username!//截取最后一个 ? 前面的字符串let index3 = str.lastIndexOf("?")let string3 = str.substring(0, index3);// 不包含 ?
console.log(string3,'string3---------')// hello? how are you doing let string33 = str.substring(0, index3 +1);// 包含 ?
console.log(string33,'string33---------')// hello? how are you doing?//截取最后一个 ? 后面的字符串let index4 = str.lastIndexOf("?")let string4 = str.substring(index4 +1, str.length);// 不包含 ?
console.log(string4,'string4----------')// username!let string44 = str.substring(index4, str.length);// 包含 ?
console.log(string44,'string44----------')// ? username!