Style Property and Values

Question

I am extracting name and values of each element in HTML DOM. For style attribute able to extract only property names not values.

My code is given below:

var elementHandles = await page.QuerySelectorAllAsync("a");
    foreach (var handle in elementHandles)
    {
        var elementStyle = await handle.GetPropertyAsync("style");
        var style = await elementStyle.JsonValueAsync();
        var output = style.ToString();
    }

This is my output:

{{
  "0": "font-family",
  "1": "font-size",
  "2": "line-height",
  "3": "color",
  "4": "text-align"
}}

This is what I am expecting:

font-family:Arial, Helvetica, sans-serif; 
font-size: 12px; 
line-height: 16px; 
color: #999999;
text-align: left

Give some more detail. Its not enough and cannot understand which problem you are getting. — Usman Khan, Nov 06 '19 at 10:10
@UsmanKhan I have an 5 anchor elements in DOM e.g. click here I am reading attributes of this element in PuppeteerSharp. Above code is not extracting css class name and its value e.g. "font-family:Arial, Helvetica, sans-serif;" instead returning "0": "font-family" — Kishan, Nov 06 '19 at 10:23

score 4 · Accepted Answer · answered Nov 06 '19 at 12:40

The problem is how the CSSStyleDeclaration is serialized. If that´s how Chromium decides to serialize that object there is nothing we can do there.

But, we can try to solve that from javascript using EvaluateFunctionAsync.

foreach (var handle in elementHandles)
{
  var style = await page.EvaluateFunctionAsync<Dictionary<string, string>>(
    "e => Object.entries(e.style).filter(i => isNaN(i[0]) && i[1]).map(i => { return { [i[0]] : i[1]}}).reduce((acc, cur) => { return {...acc, ...cur}}, {})", handle);
  var output = style.ToString();
}

Let's take a look at the javascript expression

e=> //We send the HTML element instead of the style property
  Object.entries(e.style) //We get all the property/value pairs from the CSSStyleDeclaration object
    // We want to exclude number properties (like 0,1,2) and empty values
    .filter(i => isNaN(i[0]) && i[1]) 
    //We turn them into objects
    .map(i => { return { [i[0]] : i[1]}})
    //We merge them into one single object that will be returned to C#
    .reduce((acc, cur) => { return {...acc, ...cur}}, {})

Style Property and Values

1 Answers1