The term 'sparkline' was first used by Edward Tufte, who defined a sparkline in this way:
_A sparkline is a small intense, simple, word-sized graphic with typographic resolution.
Sparklines mean that graphics are no longer cartoonish special occasions with captions and boxes,
but rather sparkline graphics can be everywhere a word or number can be: embedded in a sentence,
table, headline, map, spreadsheet, graphic. Data graphics should have the resolution of typography._
see https://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=0001OR
In html, for a chart to be embedded as Tufte describes, then that chart must be inline; that is, it should have css style
display:inline
So in order to make a genuine sparkline with echarts, we need to be able to make the echart inline.
To attempt this, we can build the echart on an inline element - e.g. <span> instead of <div>
The first complication this creates is that an inline element cannot be given height or width; so a sparkline created with echarts will need to get its height and width from the config; e.g (using svg):
echarts.init(element, null, {renderer: 'svg', height: 20, width 80})
When echarts generates the chart, we see this in the generated html:
<div style="overflow: hidden; position: relative; width: 80px; height: 20px; background: transparent; cursor: pointer;">
<svg xmlns="http://www.w3.org/2000/svg" version="1.1" baseProfile="full" width="80" height="20" style="user-select: none; position: absolute; left: 0px; top: 0px;">
This object is not inline, because the generated <div> has display:block by default, and the generated <svg> has position:absolute
We can use css to reach into this generated html and change it, like this:
<style>
.sparkline div {
display: inline
}
.sparkline svg {
position:relative !important
}
where the echart is created on a span with class sparkline:
<span class="sparkline"/>
In echarts 4.7, this workaround will give an inline chart. But it would be preferable to have this functionality available in echarts by configuration.
Add a new member display to the configuration object passed to echarts.init()
display : 'block' or 'inline' - default is 'block'
This setting causes the appropriate changes to the style attributes of the generated <div> and <svg>
e.g. sample use:
let config = {
renderer: "svg",
height: 40,
width: 100,
display: 'inline'
}
In html it will look like
<p>Here is my embedded<span id="mySparkline"/> echart</p>
where the echart is instantiated on the <span> _mySparkline_.
I think it's easy and practical to set display of echarts container(element).
There is An example on CodePen
Is it necessary to be supported by ECharts?

@plainheart : thankyou for your quick reply. You are totally right , this is much easier than I was making it out to be. The secret in your solution is the use of display:inline-block, not display:inline which I was trying to make work. @pissang , maybe this does not deserve a new feature after all - I'm satisfied with the method from @plainheart ....
I am closing this issue because the solution from @plainheart does everything needed to generate inline sparklines without any modification required to echarts.
Most helpful comment
I think it's easy and practical to set
displayof echarts container(element).There is An example on CodePen
Is it necessary to be supported by ECharts?