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Set image opacity with javascript

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[前端(javascript) 所属分类 前端(javascript) | 发布者 店小二05 | 时间 2018 | 作者 红领巾 ] 0人收藏点击收藏

Good day! In all honesty the problem is a bit more complex. I want to know why the following line of code doesn't work:

pic.style.opacity = toString((5-z)/10);

Why I think it should work ?

the opacity member variable is a string so it needs to be a string therefore as long as the "toString" method is there after the system calculates the expression it should be turned into a string and therefore it should be viable.

Note: z is an integer number which has a varying value from 0 to 4.

In case someone wants to test for themselves:

<!DOCTYPE html> <html lang="en" xmlns="http://www.w3.org/1999/xhtml"> <head> <meta charset="utf-8" /> <title></title> <style> #asd{ background-image : url(fry.jpg); margin-left:20%; margin-top:20%; height:100px; width:100px; } </style> </head> <body> <div id="asd"></div> </body> </html> <script var z = 3; function foo(){ document.getElementById("asd").style.opacity = toString((5-z)/10); } foo(); </script>

Problem courtesy of: Bloodcount

Solution

You dont' need toString .

Just do:

document.getElementById("asd").style.opacity = (5-z)/10;

You aren't using toString correct anyway. If you'd like to use it anywhere, do it that way:

var number = 42.0; var string = number.toString(10);

The 10 is optional and default. For instance you can use 2 to convert in dual system.

Solution courtesy of: dersvenhesse

Discussion

It'll work if you remove the toString. The value for opacity is a decimal value between 0.0 - 1.0

further reading: http://www.w3schools.com/css/css_image_transparency.asp

Discussion courtesy of: Jeevan Jose

You need to wait for the document to load before trying to access/set opacity for any element. Check onLoad event of javascript or $(document).ready() if you are using jQuery.

By the way - your opening script tag has a missing > sign

Discussion courtesy of: aram90

You are inadvertently calling window.toString() . The toString method is called as a method from the item you want to convert.

Also, you don't need it. Remove it.

Discussion courtesy of: Mathletics

This recipe can be found in it's original form on Stack Over Flow .

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