Share some data about some read-only properties in javaScript.

  • eg1

String values obtained using array associative methods are read-only attributes and cannot be modified

    let a = 'string';
    console.log(a[0]); //s
    a[0] = 'q';// The second line of output remains unchanged
    // Read-only attributes, unlike arrays
    console.log(a);//string
    console.log(a[0])//s
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  • eg2

CharAt () in a character object returns a specified character from a string, and an error is reported if assigned

    let a = 'string';
    console.log(a.charAt(0)) //s
    a.charAt(0) = 'q';
    //Invalid left-hand side in assignment
    The charAt() method returns the specified character from a string
    console.log(a)
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  • eg3

Htmlelement. offsetTop and htmlElement. offsetLeft are also read-only attributes. OffsetTop returns the distance of the current element relative to the top inner margin of its offsetParent element, which is a block-level element

  • eg4

In addition to offsets, get the width and height of the page’s elements, which are also read-only offsetWidth, offsetHeight, clientWidth, clientHeight

  • eg5

Methods such as getFullYear() are read-only properties, and there is usually a corresponding method that starts with set.

The purpose of setting the read-only property

The values of read-only attributes are generally the underlying data types and are stored in the stack, saving space in the heap. (Personal understanding,)