(1) Get string length
console.log(str.length); // 33
(2) Take out the characters in the specified position, such as 0, 3, 5, 9, etc
console.log(str[0], str[3], str[5], str[9]); // a a d g
(3) Find whether the specified character exists in the above string, such as: I, C, B, etc
console.log(str.indexOf('i'), str.indexOf('c'), str.indexOf('b')); // -1 -1 1
(4) Replace the specified characters, such as: G replaced by 22, SS replaced by B and so on
/*JS high-level writing of the regular expression "g / g", G is the global search*/
console.log(str.replace(/g/g, '22')); // abaasdff222222hhjjkk22fddsssss3444343
console.log(str.replace(/ss/g, 'b')); // abaasdffggghhjjkkgfddbbs3444343
(5) Intercept the string from the specified start position to the specified end position, such as: get 1-5 string
console.log(str.substr(0, 5)); // abaas
(6) Find the most frequent character and the most frequent character in the string
var newArr = {};
for (var i = 0; i < str.length; i++) {
var char = str.charAt (i) ; // charat() returns the character of the index object
if (newArr[char]) {
Newarr [char] + +; // times plus 1, "object [key] = 1" assigns value to each traversed object attribute
} else {
Newarr [char] = 1; // if it appears for the first time, the number is 1
}
}
console.log (newarr); // output a complete object, recording each character and its occurrence times
Var max = 0; // the maximum number of occurrences of the first for loop
For (VaR key in newarr) {// key is the attribute, that is, string, newarr is the object, and newarr [key] is the attribute value
if (max < newArr[key]) {
Max = newarr [key]; // max always stores the one with the largest number of times
}
}
For (VaR key in newarr) {// the second for loop finds the character corresponding to the maximum number of occurrences
if (newArr[key] == max) {
console.log ("the most characters are" + key + '\ t' + "and the number of occurrences is" + Max ");
}
}
(7) Add “@” at both ends of traversed characters
var strArr = str.split ('); // the method of splitting a string into a string array
var newStr = [];
for (var i = 0; i < strArr.length ; I + +) {// traversal
var newChar = '@' + strArr[i] + '@';
Newstr + = newchar; // connect newchar strings one by one
}
console.log(newStr);