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Summary of String Methods for JavaScript

  • 2021-07-06 09:58:10
  • OfStack

1. stringObject.charAt()

Function: Returns the subscript of a string 


var str=" This is 1 String string ";
console.log(str.charAt(0))// This

2. stringObject.charCodeAt()

Function: The method returns the Unicode encoding of the character at the specified position 


var str=" This is 1 String string ";
console.log(str.charCodeAt(0))
// This =>36825

3.String.fromCharCode()

Function: Return the corresponding character through Unicode encoding 


console.log(String.fromCharCode(36825,26159))// This is

Example: Find if a string is a number 


<body>
<input type="text" />
<input type="button" value=" Detection " />
<script>
var aInp = document.getElementsByTagName('input');

aInp[1].onclick = function () {
  
  var val = aInp[0].value;
  
  if ( detectNum(val) ) {
    alert( ' Congratulations, '+ val +' It's all numbers ' );
  } else {
    alert(' Input error ');
  }
};
function detectNum ( str ) {
  var n = 0;
  for ( var i=0; i<str.length; i++ ) {
    n = str.charCodeAt(i);
    if ( n<48 || n>57 )return false;
  }
  return true;
}
</script>
</body>

4. stringObject.indexOf()

Function: The method returns the first occurrence of a specified string value in the string.
Parameter: str. indexOf (find value, start looking for subscript), which returns-1 if the string value to retrieve does not appear.

Example: Return to find the subscript of the corresponding character 


  <script>
  var str = 'xsxsxscdecdcdxsxsxs';
  var num = 0;
  var s = 'xs';
  var arr = [];
  for (; str.indexOf(s, num) != -1;) {
    num = str.indexOf(s, num) + s.length
    arr.push(num)
  }
  console.log(arr)
  </script>

5. stringObject.lastIndexOf()

Function: Find the first occurrence of a specified string value in the string from back to front

6. stringObject.substring()

Function: The method is used to extract the characters between two specified subscripts in a string.

7. stringObject.toUpperCase()

Function: Letters are converted to uppercase

8. stringObject.toLowerCase()

Function: Letters are converted to lowercase

9.stringObject.split()

Function: The method is used to divide a string into a string array
Parameter: (by what character to truncate and to what bit to keep the array)

Three usages 


var str="121314";

str.split("") //[1,2,1,3,1,4];

str.split("1")//[ ,2,3,4];

str.split("",2)//[1,2]
10.arrObject.join()

Function: The method is used to put all the elements in the array into a string. Elements are separated by the specified separator

Two usages 


var arr = [1,2,3];
arr.join("")//123
arr.join("-")//1-2-3

Example: Highlight the keywords you are looking for 


  <input type="text" id="oin" />
  <button> Button </button>
  var oin = document.getElementById("oin");
  var obtn = document.getElementsByTagName('button')[0];
  var str = "arguments The length of an object is determined by the number of arguments, not the number of formal arguments. 
   A formal parameter is a variable that re-opens memory space within a function, but it is the same as arguments Object 
   Memory space does not overlap. For arguments And values exist, the two values are synchronized 
   , but for one of the 1 If there is no value, the values will not be synchronized for this no value case. 
   The following code can be verified. ";
  var h = "";
  obtn.onclick = function() {
    if (oin.value == "") {
      alert(" Enter blank ");
      return false
    }
    var s = oin.value;
    if (str.indexOf(s) == -1) {
      alert(" There is no such number ");
      return false
    }
    var m = '<span style="background-color:red">' + s + '</span>';
    str = str.split(s);
    h = str.join(m)
    document.body.innerHTML=h
  }

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