string 操作总结

1.String.prototype.slice The slice() method extracts a section of a string and returns a new string.

var str1 = 'The morning is upon us.', // the length of str1 is 23.
    str2 = str1.slice(1, 8),
    str3 = str1.slice(4, -2),
    str4 = str1.slice(12),
    str5 = str1.slice(30);
console.log(str2); // OUTPUT: he morn
console.log(str3); // OUTPUT: morning is upon u
console.log(str4); // OUTPUT: is upon us.
console.log(str5); // OUTPUT: ""

2.String.prototype.split() The split() method splits a String object into an array of strings by separating the string into substrings.

var myString = 'Hello World. How are you doing?';
var splits = myString.split(' ', 3);

console.log(splits);
//["Hello", "World.", "How"]

3.String.prototype.indexOf() The indexOf() method returns the index within the calling String object of the first occurrence of the specified value, starting the search at fromIndex. Returns -1 if the value is not found.

'Blue Whale'.indexOf('Blue');     // returns  0
'Blue Whale'.indexOf('Blute');    // returns -1
'Blue Whale'.indexOf('Whale', 0); // returns  5
'Blue Whale'.indexOf('Whale', 5); // returns  5
'Blue Whale'.indexOf('');         // returns  0
'Blue Whale'.indexOf('', 9);      // returns  9
'Blue Whale'.indexOf('', 10);     // returns 10
'Blue Whale'.indexOf('', 11);     // returns 10

4.String.prototype.lastIndexOf() The lastIndexOf() method returns the index within the calling String object of the last occurrence of the specified value, searching backwards from fromIndex. Returns -1 if the value is not found.

'canal'.lastIndexOf('a');     // returns 3
'canal'.lastIndexOf('a', 2);  // returns 1
'canal'.lastIndexOf('a', 0);  // returns -1
'canal'.lastIndexOf('x');     // returns -1
'canal'.lastIndexOf('c', -5); // returns 0
'canal'.lastIndexOf('c', 0);  // returns 0
'canal'.lastIndexOf('');      // returns 5
'canal'.lastIndexOf('', 2);   // returns 2

5.String.prototype.search() The search() method executes a search for a match between a regular expression and this String object.

//The following example logs a message which depends on the success of the test.
function testinput(re, str) {
  var midstring;
  if (str.search(re) != -1) {
    midstring = ' contains ';
  } else {
    midstring = ' does not contain ';
  }
  console.log(str + midstring + re);
}

6.String.prototype.substring() The substring() method returns a subset of a string between one index and another, or through the end of the string.

var anyString = 'Mozilla';

// Displays 'Moz'
console.log(anyString.substring(0, 3));
console.log(anyString.substring(3, 0));

// Displays 'lla'
console.log(anyString.substring(4, 7));
console.log(anyString.substring(4));
console.log(anyString.substring(7, 4));

// Displays 'Mozill'
console.log(anyString.substring(0, 6));

// Displays 'Mozilla'
console.log(anyString.substring(0, 7));
console.log(anyString.substring(0, 10));

7.String.prototype.substr() The substr() method returns the characters in a string beginning at the specified location through the specified number of characters.

var str = 'abcdefghij';

console.log('(1, 2): '   + str.substr(1, 2));   // '(1, 2): bc'
console.log('(-3, 2): '  + str.substr(-3, 2));  // '(-3, 2): hi'
console.log('(-3): '     + str.substr(-3));     // '(-3): hij'
console.log('(1): '      + str.substr(1));      // '(1): bcdefghij'
console.log('(-20, 2): ' + str.substr(-20, 2)); // '(-20, 2): ab'
console.log('(20, 2): '  + str.substr(20, 2));  // '(20, 2): '

8.String.prototype.concat() The concat() method combines the text of one or more strings and returns a new string.

var hello = 'Hello, ';
console.log(hello.concat('Kevin', ' have a nice day.'));

/* Hello, Kevin have a nice day. */

String.prototype.toLowerCase() : The toLowerCase() method returns the calling string value converted to lower case.
String.prototype.toUpperCase() : The toUpperCase() method returns the calling string value converted to upper case.