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Fixes #437 -- add an 'immediate' parameter to _.debounce.

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This commit is contained in:
Jeremy Ashkenas
2012-01-30 10:53:46 -05:00
parent 1bb750508d
commit 5533c12033
2 changed files with 19 additions and 3 deletions
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14
test/functions.js
View File

@@ -146,6 +146,20 @@ $(document).ready(function() {
_.delay(function(){ ok(counter == 1, "incr was debounced"); start(); }, 220); _.delay(function(){ ok(counter == 1, "incr was debounced"); start(); }, 220);
}); });
asyncTest("functions: debounce asap", 2, function() {
var counter = 0;
var incr = function(){ counter++; };
var debouncedIncr = _.debounce(incr, 50, true);
debouncedIncr(); debouncedIncr(); debouncedIncr();
equal(counter, 1, 'incr was called immediately');
setTimeout(debouncedIncr, 30);
setTimeout(debouncedIncr, 60);
setTimeout(debouncedIncr, 90);
setTimeout(debouncedIncr, 120);
setTimeout(debouncedIncr, 150);
_.delay(function(){ equal(counter, 1, "incr was debounced"); start(); }, 220);
});
test("functions: once", function() { test("functions: once", function() {
var num = 0; var num = 0;
var increment = _.once(function(){ num++; }); var increment = _.once(function(){ num++; });

8
underscore.js
View File

@@ -548,15 +548,17 @@
// Returns a function, that, as long as it continues to be invoked, will not // Returns a function, that, as long as it continues to be invoked, will not
// be triggered. The function will be called after it stops being called for // be triggered. The function will be called after it stops being called for
// N milliseconds. // N milliseconds. If `immediate` is passed, trigger the function on the
_.debounce = function(func, wait) { // leading edge, instead of the trailing.
_.debounce = function(func, wait, immediate) {
var timeout; var timeout;
return function() { return function() {
var context = this, args = arguments; var context = this, args = arguments;
var later = function() { var later = function() {
timeout = null; timeout = null;
func.apply(context, args); if (!immediate) func.apply(context, args);
}; };
if (immediate && !timeout) func.apply(context, args);
clearTimeout(timeout); clearTimeout(timeout);
timeout = setTimeout(later, wait); timeout = setTimeout(later, wait);
}; };