The difference between getelementbyid,getelementsbyname,getelementsbytagname

1, getElementById




returns the first in the same ID object, in the order in which the page appears , or null if there are no eligible objects

Example
document.getElementById ("Id1"). Value;

2, Getelementsbyname

Function: Finds an array of elements of the same name by the names of the elements
Syntax: Document.getelementsbyname (name)
Parameter: Name: Required option is string
Return value: Array Object ; If there are no eligible objects, an empty array is returned, in the order in which they appear in the page

Example
Document. getelementsbyname ("name1") [0]. value;  Gets the element of the same name that you want

3, getElementsByTagName

Function: Query by HTML tag name, return an array of the same tag element
Syntax: Object.getelementsbytagname (tagname) object can be document or event.srcElement.parentElement, etc.
Parameter: tagname: The required option is a string, which is retrieved according to the HTML tag.
Return value: Array Object ; If there are no eligible objects, an empty array is returned, in the order in which they appear in the page


Summarize:

The 1.getElementByID return value is the first one in the ID object
2.getElementsByName and getElementsByTagName return an array object

The difference between getelementbyid,getelementsbyname,getelementsbytagname