javascript - Angular 的 copy 函数，看不太懂，求分析下
function copy(source, destination, stackSource, stackDest) {
if (isWindow(source) || isScope(source)) {
throw ngMinErr('cpws',
"Can't copy! Making copies of Window or Scope instances is not supported.");
}
if (!destination) {
destination = source;
if (source) {
if (isArray(source)) {
destination = copy(source, [], stackSource, stackDest);
} else if (isDate(source)) {
destination = new Date(source.getTime());
} else if (isRegExp(source)) {
destination = new RegExp(source.source, source.toString().match(/[^\/]*$/)[0]);
destination.lastIndex = source.lastIndex;
} else if (isObject(source)) {
destination = copy(source, {}, stackSource, stackDest);
}
}
} else {
if (source === destination) throw ngMinErr('cpi',
"Can't copy! Source and destination are identical.");
stackSource = stackSource || [];
stackDest = stackDest || [];
if (isObject(source)) {
var index = indexOf(stackSource, source);
if (index !== -1) return stackDest[index];
stackSource.push(source);
stackDest.push(destination);
}
var result;
if (isArray(source)) {
destination.length = 0;
for ( var i = 0; i < source.length; i++) {
result = copy(source[i], null, stackSource, stackDest);
if (isObject(source[i])) {
stackSource.push(source[i]);
stackDest.push(result);
}
destination.push(result);
}
} else {
var h = destination.$$hashKey;
if (isArray(destination)) {
destination.length = 0;
} else {
forEach(destination, function(value, key) {
delete destination[key];
});
}
for ( var key in source) {
result = copy(source[key], null, stackSource, stackDest);
if (isObject(source[key])) {
stackSource.push(source[key]);
stackDest.push(result);
}
destination[key] = result;
}
setHashKey(destination,h);
}
}
return destination;
}
