//`build` is a recursive function that manages creation/diffing/removal of DOM elements based on comparison between `data` and `cached`
//`parentElement` is a DOM element used for W3C DOM API calls
//`parentTag` is only used for handling a corner case for textarea values
//`parentCache` is used to remove nodes in some multi-node cases
//`parentIndex` and `index` are used to figure out the offset of nodes. They're artifacts from before arrays started being flattened and are likely refactorable
//`data` and `cached` are, respectively, the new and old nodes being diffed
//`shouldReattach` is a flag indicating whether a parent node was recreated (if so, and if this node is reused, then this node must reattach itself to the new parent)
//`editable` is a flag that indicates whether an ancestor is contenteditable
//`namespace` indicates the closest HTML namespace as it cascades down from an ancestor
//`configs` is a list of config functions to run after the topmost `build` call finishes running
//there's logic that relies on the assumption that null and undefined data are equivalent to empty strings
//- this prevents lifecycle surprises from procedural helpers that mix implicit and explicit return statements
if(einstanceofSyntaxError)thrownewSyntaxError("Could not parse HTTP response. See http://lhorie.github.io/mithril/mithril.request.html#using-variable-data-formats")
//`build` is a recursive function that manages creation/diffing/removal of DOM elements based on comparison between `data` and `cached`
//the diff algorithm can be summarized as this:
//1 - compare `data` and `cached`
//2 - if they are different, copy `data` to `cached` and update the DOM based on what the difference is
//3 - recursively apply this algorithm for every array and for the children of every virtual element
//the `cached` data structure is essentially the same as the previous redraw's `data` data structure, with a few additions:
//- `cached` always has a property called `nodes`, which is a list of DOM elements that correspond to the data represented by the respective virtual element
//- in order to support attaching `nodes` as a property of `cached`, `cached` is *always* a non-primitive object, i.e. if the data was a string, then cached is a String instance. If data was `null` or `undefined`, cached is `new String("")`
//- `cached also has a `configContext` property, which is the state storage object exposed by config(element, isInitialized, context)
//- when `cached` is an Object, it represents a virtual element; when it's an Array, it represents a list of elements; when it's a String, Number or Boolean, it represents a text node
//`parentElement` is a DOM element used for W3C DOM API calls
//`parentTag` is only used for handling a corner case for textarea values
//`parentCache` is used to remove nodes in some multi-node cases
//`parentIndex` and `index` are used to figure out the offset of nodes. They're artifacts from before arrays started being flattened and are likely refactorable
//`data` and `cached` are, respectively, the new and old nodes being diffed
//`shouldReattach` is a flag indicating whether a parent node was recreated (if so, and if this node is reused, then this node must reattach itself to the new parent)
//`editable` is a flag that indicates whether an ancestor is contenteditable
//`namespace` indicates the closest HTML namespace as it cascades down from an ancestor
//`configs` is a list of config functions to run after the topmost `build` call finishes running
//there's logic that relies on the assumption that null and undefined data are equivalent to empty strings
//- this prevents lifecycle surprises from procedural helpers that mix implicit and explicit return statements (e.g. function foo() {if (cond) return m("div")}
//- it simplifies diffing code
//data.toString() is null if data is the return value of Console.log in Firefox
if(cached.tag)cached={};//if constructor creates a virtual dom element, use a blank object as the base cached node instead of copying the virtual el (#277)
cached.nodes=[]
}
if(dataType===ARRAY){
//recursively flatten array
for(vari=0,len=data.length;i<len;i++){
if(type.call(data[i])===ARRAY){
data=data.concat.apply([],data);
i--//check current index again and flatten until there are no more nested arrays at that index
//a modified version of Promiz.js, which does not conform to Promises/A+ for two reasons:
//1) `then` callbacks are called synchronously (because setTimeout is too slow, and the setImmediate polyfill is too big
//2) throwing subclasses of Error cause the error to be bubbled up instead of triggering rejection (because the spec does not account for the important use case of default browser error handling, i.e. message w/ line number)
