Created
February 16, 2010 06:38
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(function(global){ | |
var undef; | |
function Promise(){} | |
Promise.prototype.constructor = Promise; | |
global.promise = function(cb) { | |
var publicAPI, queue = [], old_ret, promise_fulfilled = false; | |
function fulfill(val) { | |
var ret_val = val; | |
if (typeof ret_val != "undefined") old_ret = ret_val; | |
try { | |
return val; | |
} | |
finally { | |
for (var i=0,len=queue.length; i<len; i++) { | |
if (typeof ret_val != "undefined") old_ret = ret_val; | |
ret_val = queue[0].call(publicAPI,ret_val); | |
if (typeof ret_val == "undefined") { ret_val = old_ret; } | |
else if (ret_val.constructor !== Promise) old_ret = ret_val; // lame, V8 "instanceof" currently broken | |
queue.shift(); | |
if (ret_val.constructor === Promise) { // lame, V8 "instanceof" currently broken | |
promise_fulfilled = false; | |
ret_val.then(function(P){ promise_fulfilled = true; return (old_ret = fulfill(P.value)); }); | |
break; | |
} | |
} | |
} | |
} | |
publicAPI = new Promise(); | |
publicAPI.then = function(cb){ | |
queue[queue.length] = function(val){ return cb.call(publicAPI,{value:val}); }; | |
if (promise_fulfilled) fulfill(old_ret); | |
return publicAPI; | |
}; | |
cb.call(publicAPI,{fulfill:function(val){ | |
promise_fulfilled = true; | |
fulfill.call(publicAPI,val); | |
},value:undef}); | |
return publicAPI; | |
}; | |
})(window); |
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var Load = function(src,cb) { | |
var xhr = new XMLHttpRequest(); | |
xhr.open("GET",src); | |
xhr.onreadystatechange = function(){ | |
if (xhr.readyState == 4) { | |
cb(xhr.responseText); | |
} | |
}; | |
xhr.send(); | |
}; |
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promise(function(P){ | |
Load("abc.js",P.fulfill); | |
}) | |
.then(function(P){ | |
return promise(function(P2){ | |
setTimeout(function(){ | |
P2.fulfill(P.value); | |
},2000); | |
}); | |
}) | |
.then(function(P){ | |
return P.value.toUpperCase(); | |
}) | |
.then(function(P){ | |
return promise(function(P2) { | |
setTimeout(function(){ | |
P2.fulfill(P.value); | |
},1000); | |
}) | |
.then(function(P){ | |
return P.value+"!"; | |
}); | |
}) | |
.then(function(P){ | |
// do nothing -- silently pass along P.value | |
}) | |
.then(function(P){ | |
console.log(P.value); | |
}); |
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promise(function(P){ | |
P.fulfill("Hello"); | |
}) | |
.then(function(P){ | |
return promise(function(P2){ | |
P2.fulfill(P.value+" World"); | |
}) | |
.then(function(P){ | |
return P.value.toUpperCase(); | |
}); | |
}) | |
.then(function(P){ | |
console.log(P.value+"!"); | |
}); |
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