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Summary of JavaScript string methods

高洛峰Original: 2017-01-14 10:32:281049browse

1. stringObject.charAt()

Function: Return the subscript of the string

var str="这是一串字符串";
console.log(str.charAt(0))//这

2. stringObject.charCodeAt()

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

var str="这是一串字符串";
console.log(str.charCodeAt(0))
//这=>36825

3.String.fromCharCode()

Function: Pass Unicode encoding returns the corresponding characters

console.log(String.fromCharCode(36825,26159))//这是

Example question: Find whether a string is a number

<body>
<input type="text" />
<input type="button" value="检测" />
<script>
var aInp = document.getElementsByTagName(&#39;input&#39;);
 
aInp[1].onclick = function () {
   
  var val = aInp[0].value;
   
  if ( detectNum(val) ) {
    alert( &#39;恭喜，&#39;+ val +&#39;全是数字&#39; );
  } else {
    alert(&#39;输入有误&#39;);
  }
};
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: This method can return the position where a specified string value first appears in the string.
Parameters: str.indexOf (search value, start searching for subscript), if the string value to be retrieved does not appear, this method returns -1.

Example: Return the subscript where the corresponding character appears

<script>
var str = &#39;xsxsxscdecdcdxsxsxs&#39;;
var num = 0;
var s = &#39;xs&#39;;
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: from back to front Find the position where a specified string value first appears in the string

6. stringObject.substring()

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

7. stringObject.toUpperCase()

Function: Convert letters to uppercase

8. stringObject.toLowerCase()

Function: Convert letters to lowercase

9.stringObject.split()

Function: The method is used to split a string into a string array
Parameters: (What Character interception, retaining the number of 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 delimiter

Two usages

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

Example: Highlight the searched keyword

<input type="text" id="oin" />
<button>按钮</button>
var oin = document.getElementById("oin");
var obtn = document.getElementsByTagName(&#39;button&#39;)[0];
var str = "arguments对象的长度是由实参个数而不是形参个数决定的。
形参是函数内部重新开辟内存空间存储的变量，但是其与arguments对象
内存空间并不重叠。对于arguments和值都存在的情况下，两者值是同步的
，但是针对其中一个无值的情况下，对于此无值的情形值不会得以同步。
如下代码可以得以验证。";
var h = "";
obtn.onclick = function() {
  if (oin.value == "") {
    alert("输入为空");
    return false
  }
  var s = oin.value;
  if (str.indexOf(s) == -1) {
    alert("没有这个数字");
    return false
  }
  var m = &#39;<span style="background-color:red">&#39; + s + &#39;</span>&#39;;
  str = str.split(s);
  h = str.join(m)
  document.body.innerHTML=h
}

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