CharacterData: substringData() method
  The substringData() method of the CharacterData interface
  returns a portion of the existing data,
  starting at the specified index
  and extending for a given number of characters afterwards.
Syntax
js
  domString = characterData.substringData(offset, count)
Parameters
- offset
- 
    The index of the first character to include in the returned substring. 0is the first character of the string.
- count
- 
    The number of characters to return. 
Return value
A string with the substring.
Exceptions
- IndexSizeError- DOMException
- 
    Thrown if offset+countis larger than the length of the contained data.
Specifications
| Specification | 
|---|
| DOM Standard # dom-characterdata-substringdata | 
Browser compatibility
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