无法理解handlebars.js上下文

Question

I'm having trouble understanding how context works in handlebars.js, specifically the "../" notation. This is best exemplified by the jsfiddle I put together:

http://jsfiddle.net/accelerate/AwChe/

Context:

"rootvar": "hi",
"mydata": [{
    "renderme": true,
    "mytext": "bye"
}]

Template:

rootvar = {{{rootvar}}} (should be "hi")<br/>
{{#each mydata}}
<br/>In mydata...<br/>
rootvar = {{{rootvar}}} (should be empty)<br/>
rootvar = {{{../rootvar}}} (should be "hi")<br/>
mytext = {{{mytext}}} (should be "bye")<br/>
{{#if renderme}}
<br/>In renderme...<br/>
rootvar = {{{rootvar}}} (should be empty)<br/>
rootvar = {{{../rootvar}}} (should be empty)<br/>
rootvar = {{{../../rootvar}}} (should be "hi")<br/>
mytext = {{{mytext}}} (should be empty!!)<br/>
mytext = {{{../mytext}}} (should be "bye")<br/>
{{/if}}
{{/each}}

Output:

rootvar = hi (should be "hi")

In mydata...
rootvar = (should be empty)
rootvar = hi (should be "hi")
mytext = bye (should be "bye")

In renderme...
rootvar = (should be empty)
rootvar = (should be empty)
rootvar = hi (should be "hi")
mytext = bye (should be empty!!)
mytext = bye (should be "bye")

So in other words, I have an #if statement nested within an #each statement. I can see why I need to use "../../rootvar" to access "rootvar." What I don't understand is why I don't need to do do a "../" to access other variables within the current mydata element. Shouldn't I need to go to the #if's parent context to access "mytext", like I do for "rootvar"? And if I don't, then why does "../mytext" also work?

Answer 1

this is normal with #if helper because it preserve the context.

//here context is:
//  "rootvar": "hi",
//  "mydata": [{
//  "renderme": true,
//  "mytext": "bye" }]
rootvar = {{{rootvar}}} (should be "hi")<br/>
{{#each mydata}}
// here `each` will change the context to each item in 'mydata' so it becomes
//   { "renderme": true,
//     "mytext": "bye" }
<br/>In mydata...<br/>
rootvar = {{{rootvar}}} (should be empty)<br/>
rootvar = {{{../rootvar}}} (should be "hi")<br/>
mytext = {{{mytext}}} (should be "bye")<br/>
{{#if renderme}}
// now `if` will create new context but it is the same as the parent context
//     { "renderme": true,
//     "mytext": "bye" }
<br/>In renderme...<br/>
rootvar = {{{rootvar}}} (should be empty)<br/>
rootvar = {{{../rootvar}}} (should be empty)<br/>
rootvar = {{{../../rootvar}}} (should be "hi")<br/>
mytext = {{{mytext}}} (should be "bye")<br/>
mytext = {{{../mytext}}} (should be "bye")<br/>
{{/if}}
{{/each}}

see this github issue for more details.