gistのrawコンテンツを取得する

retrieveGistContent.js

/*
 * https://gist.github.com/username/123456 のようなURLを受け取ると、そのrawコンテンツを取得しcallbackに渡す
 */
function retrieveGistContent( gistUrl, callback ){
	var t = "";
	var _write = document.write;
	if( !/^https:\/\/gist\.github\.com\/[^\/]+\/[\da-fA-F]+$/.test( gistUrl ) ) return;
	document.write = function(){
		for( var i = 0; i < arguments.length; i++ ){
			t += arguments[ i ];
		}
	};
	var elm = document.createElement( "script" );
	elm.onload = function(){
		var m = /(https:\/\/gist\.github\.com\/[^\/]+\/[\da-fA-F]+\/raw\/[\da-fA-F]+\/[^\\"]+)/.exec( t );
		if( m !== null ){
			var url = m[ 1 ].replace( /^https:\/\/gist\.github/, "https://gist.githubusercontent" );
			var xhr = new XMLHttpRequest();
			xhr.open( "GET", url, true );
			xhr.onload = function(){
				callback( xhr.responseText );
			};
			xhr.send( null  );
		}
		document.write = _write;
	};
	elm.src = gistUrl + ".js";
	document.body.appendChild( elm );
}