{"id":18,"date":"2006-11-07T01:25:04","date_gmt":"2006-11-07T09:25:04","guid":{"rendered":"http:\/\/porkrind.org\/missives2\/?p=18"},"modified":"2015-02-20T22:18:53","modified_gmt":"2015-02-21T06:18:53","slug":"efficient-javascript-or-inefficient-browser","status":"publish","type":"post","link":"https:\/\/porkrind.org\/missives\/efficient-javascript-or-inefficient-browser\/","title":{"rendered":"Efficient JavaScript or Inefficient Browser?"},"content":{"rendered":"

I caught this article<\/a> on Reddit<\/a> this weekend and had definite mixed feelings about it. Many of their suggestions were obviously good ideas\u2014calling SetTimeout()<\/tt> with a string is obviously stupid, as are 90% of the possible uses of eval()<\/tt> and Function()<\/tt>. The advice on what causes the DOM to repaint and reflow was interesting and informative.<\/p>\n

It would have been a really good article except that some of their advice seemed weak. Some of what was masquerading as optimization “advice” seemed more like work-arounds for a substandard javascript implementation.<\/p>\n

Take this for example:<\/p>\n

\n
var min = Math.min(a,b);\r\nA.push(v);\r\n<\/code><\/pre>\n
These alternatives provide the same functionality, while performing better:<\/p>\n
var min = a < b ? a : b;\r\nA[A.length] = v;\r\n<\/code><\/pre>\n<\/blockquote>\n
Yes, I can see in someone’s world that might perform better. But come on, the compiler\/scanner should be able to produce the equivalent code. Anything less is a failing of your browser and not an “unoptimized” program. Do you really expect people to crappify their programs because your browser can’t properly optimize javascript for you?<\/p>\n
“Well,” I hear you say, “it’s interpreted<\/em>, not compiled<\/em>.” To which I say, yeah, well there’s your first problem. Fix that before telling me that I need to use stupid constructs to make my program go fast.<\/p>\n
Here’s another example:<\/p>\n
This example requires the script engine to create 21 new string objects, once for each time the length property is accessed, and once each time the charAt method is called:<\/p>\n
var s = '0123456789';\r\nfor( var i = 0; i < s.length; i++ ) {\r\n  s.charAt(i);\r\n}<\/code><\/pre>\n
This equivalent example creates just a single object, and will perform better as a result:<\/p>\n
var s = new String('0123456789');\r\nfor( var i = 0; i < s.length; i++ ) {\r\n  s.charAt(i);\r\n}\r\n<\/code><\/pre>\n<\/blockquote>\n
Again, this strikes me as being a failing of the compiler. I see no reason why the browser should instantiate a string object just to call its length(). A little bit of hard coding in your implementation can optimize that to a strlen()<\/tt> call or better\u2014No object instantiation at all. What if someone overrode String.prototype.length()? That’s one if<\/tt> statement in C and some fallback code. Again, I don’t think my<\/em> program should suffer because your<\/em> browser doesn’t properly optimize things.<\/p>\n
But then again, maybe I’m just crazy.<\/p>\n","protected":false},"excerpt":{"rendered":"
I caught “this article”:http:\/\/dev.opera.com\/articles\/view\/48\/ on “Reddit”:http:\/\/reddit.com this weekend and had definite mixed feelings about it. Many of their suggestions were obviously good ideas. But some of what was masquerading as optimization “advice” seemed more like work-arounds for a substandard javascript implementation.<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[3],"tags":[13],"class_list":["post-18","post","type-post","status-publish","format-standard","hentry","category-software","tag-javascript"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/porkrind.org\/missives\/wp-json\/wp\/v2\/posts\/18","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/porkrind.org\/missives\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/porkrind.org\/missives\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/porkrind.org\/missives\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/porkrind.org\/missives\/wp-json\/wp\/v2\/comments?post=18"}],"version-history":[{"count":8,"href":"https:\/\/porkrind.org\/missives\/wp-json\/wp\/v2\/posts\/18\/revisions"}],"predecessor-version":[{"id":495,"href":"https:\/\/porkrind.org\/missives\/wp-json\/wp\/v2\/posts\/18\/revisions\/495"}],"wp:attachment":[{"href":"https:\/\/porkrind.org\/missives\/wp-json\/wp\/v2\/media?parent=18"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/porkrind.org\/missives\/wp-json\/wp\/v2\/categories?post=18"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/porkrind.org\/missives\/wp-json\/wp\/v2\/tags?post=18"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}