Promisified return value

[AABoyles]

Resolves #204

[exupero]

Why are these return statements necessary?

[AABoyles]

They aren't, just experiment cruft. Sorry about that!

[exupero]

Can requireDomNode(el) be left outside the promise?

[AABoyles]

Probably, but I think that would be a step in the wrong direction. It looks like requireDomNode is basically just to halt execution if el isn't a DOM node. If we're going to throw an error when we're returning a promise, best practice would be to call reject instead. Something like this:

Suggested change

	requireDomNode(el);
	return new Promise((resolve, reject) => {
	if(isDomNode(el)){
	resolve();
	} else {
	reject();
	}
	});

[exupero]

I think svgAsDataUri already returns a promise.

[AABoyles]

Yes, but download does not, and I need to make sure that my callback fires after the entire stack is called.

[exupero]

I think svgAsPngUri already returns a promise.

[AABoyles]

Yes, but download does not, and I need to make sure that my callback fires after the entire stack is called.

[exupero]

Thanks for the feedback. Does something like this work?

diff --git a/src/saveSvgAsPng.js b/src/saveSvgAsPng.js
index 620af07..30cc81c 100644
--- a/src/saveSvgAsPng.js
+++ b/src/saveSvgAsPng.js
@@ -20,6 +20,11 @@
   const requireDomNode = el => {
     if (!isElement(el)) throw new Error(`an HTMLElement or SVGElement is required; got ${el}`);
   };
+  const requireDomNodePromise = el =>
+    new Promise((resolve, reject) => {
+      if (isElement(el)) resolve(el)
+      else reject(new Error(`an HTMLElement or SVGElement is required; got ${el}`));
+    })
   const isExternal = url => url && url.lastIndexOf('http',0) === 0 && url.lastIndexOf(window.location.host) === -1;
 
   const getFontMimeTypeFromUrl = fontUrl => {
@@ -367,12 +372,14 @@
   };
 
   out$.saveSvg = (el, name, options) => {
-    requireDomNode(el);
-    out$.svgAsDataUri(el, options || {}, uri => out$.download(name, uri));
+    requireDomNodePromise(el)
+      .then(out$.svgAsDataUri(el, options || {}))
+      .then(uri => out$.download(name, uri));
   };
 
   out$.saveSvgAsPng = (el, name, options) => {
-    requireDomNode(el);
-    out$.svgAsPngUri(el, options || {}, uri => out$.download(name, uri));
+    requireDomNodePromise(el)
+      .then(out$.svgAsPngUri(el, options || {}))
+      .then(uri => out$.download(name, uri));
   };
 })();

download appears to be synchronous, so the promise should only complete once the link has been clicked and removed.

[AABoyles]

That looks great! Thanks for working with me on this!

[exupero]

I just published version 1.4.9 with these changes. Let me know if they work for you.