NEW 167549
Invoking generated callback should allow setting the `this` object 
https://bugs.webkit.org/show_bug.cgi?id=167549
Summary Invoking generated callback should allow setting the `this` object
Joseph Pecoraro
Reported 2017-01-28 02:28:42 PST
Summary: Invoking callback should allow setting the `this` object. Cases like IntersectionObserver, PerformanceObserver and MutationObserver. For example PerformanceObserver: <script> let observer = new PerformanceObserver(function f(list, obs) { console.log("this", this); // Expected `observer`, was `arguments.callee` }) observer.observe({entryTypes: ["mark"]}); performance.mark("mark1"); </script> The callbacks and their interface are autogenerated from WebIDL and have a handleEvent method. Seems we need a way to the `this` object in some cases. (Probably not all, requestAnimationFrame for example prolly doesn't have the same constraints). Currently this works with MutationObserver, which has a custom implementation of the callback (not generated). See JSMutationCallback. <body> <div id="my-div"></div> <script> var target = document.getElementById("my-div"); var observer = new MutationObserver(function(mutations) { console.log("this", this); // Expected `observer` but is `arguments.callee` }); observer.observe(target, {childList: true}); target.appendChild( document.createElement("span") ); </script>
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Ahmad Saleem
Comment 1 2022-09-03 06:30:00 PDT
JSFiddle - https://jsfiddle.net/79xqnct6/ *** Chrome Canary 107 *** "this", [object PerformanceObserver] { disconnect: function disconnect() { [native code] }, observe: function observe() { [native code] }, takeRecords: function takeRecords() { [native code] } } *** Firefox Nightly 106 *** "this", [object PerformanceObserver] { disconnect: function disconnect() { [native code] }, observe: function observe() { [native code] }, takeRecords: function takeRecords() { [native code] } } *** Safari Technology Preview 152 *** "this", [object PerformanceObserver] { disconnect: function disconnect() { [native code] }, observe: function observe() { [native code] }, takeRecords: function takeRecords() { [native code] } } _________________ Is anything needed here? Thanks!
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