“SyntaxError: Unexpected EOF” when evaluating JavaScript in iOS UIWebView

Question

I keep getting this error in JavaScript when trying to pass some JSON to a UIWebView:

SyntaxError: Unexpected EOF

There is no line number or filename available in window.onerror but I've already checked all referenced files, and they are fine.

I'm using MonoTouch EvaluateJavaScript method which is equivalent to ObjC stringByEvaluatingJavaScriptFromString::

webView.EvaluateJavascript(
    "Viewer.init($('#page'), " + json.ToString() + ");"
);

It works just fine on “simple” JSON input but breaks at larger objects.
What could go wrong?

Willster · Accepted Answer · 2014-04-02T12:16:18.087

29

Before passing an NSString to a UIWebView, be sure to escape newlines as well as single/double quotes:

NSString *html = @"<div id='my-div'>Hello there</div>";

html = [html stringByReplacingOccurrencesOfString:@"\'" withString:@"\\\'"];
html = [html stringByReplacingOccurrencesOfString:@"\"" withString:@"\\\""];
html = [html stringByReplacingOccurrencesOfString:@"\n" withString:@"\\n"];
html = [html stringByReplacingOccurrencesOfString:@"\r" withString:@""];

NSString *javaScript = [NSString stringWithFormat:@"injectSomeHtml('%@');", html];
[_webView stringByEvaluatingJavaScriptFromString:javaScript];

edited Apr 02 '14 at 12:16

answered Apr 02 '14 at 12:09

Willster

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In my case (macOS 10.11+, Swift 4.x), replacing `\'` with `\\\'` is unnecessary. – Ke Yang Feb 07 '18 at 07:11
for Swift 5.x, use html.replacingOccurrences(of: "\n", with: "\\n") – Vivek Sep 05 '22 at 13:18

score 6 · Answer 2 · edited May 23 '17 at 12:10

6

Apparently, I forgot to escape newlines in JSON, and thus created an “unexpected EOF” for UIWebView.

edited May 23 '17 at 12:10

Community

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answered Jul 13 '12 at 21:01

Dan Abramov

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“SyntaxError: Unexpected EOF” when evaluating JavaScript in iOS UIWebView

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