syscall/js: extend ValueOf to support arrays and objects

This commits adds []interface{} and map[string]interface{} as quick
ways to create JavaScript arrays and objects. They correspond to the
JavaScript notations [...] and {...}. A type alias can be used for
a concise notation.

Change-Id: I98bb08dbef1e0f3bd3d65c732d6b09e1520026ba
Reviewed-on: https://go-review.googlesource.com/126855
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/syscall/js/js.go b/src/syscall/js/js.go
index 5deef35c2bb36f5a780eb6a3df3cd4f2a131f476..336586ca2dd1831d9e695d2d5fb2d9fd5a172fd7 100644 (file)
--- a/src/syscall/js/js.go
+++ b/src/syscall/js/js.go
@@ -64,6 +64,9 @@ var (
        valueGlobal    = predefValue(5)
        memory         = predefValue(6) // WebAssembly linear memory
        jsGo           = predefValue(7) // instance of the Go class in JavaScript
+
+       objectConstructor = valueGlobal.Get("Object")
+       arrayConstructor  = valueGlobal.Get("Array")
 )
 
 // Undefined returns the JavaScript value "undefined".
@@ -83,15 +86,17 @@ func Global() Value {
 
 // ValueOf returns x as a JavaScript value:
 //
-//  | Go                    | JavaScript            |
-//  | --------------------- | --------------------- |
-//  | js.Value              | [its value]           |
-//  | js.TypedArray         | [typed array]         |
-//  | js.Callback           | function              |
-//  | nil                   | null                  |
-//  | bool                  | boolean               |
-//  | integers and floats   | number                |
-//  | string                | string                |
+//  | Go                     | JavaScript             |
+//  | ---------------------- | ---------------------- |
+//  | js.Value               | [its value]            |
+//  | js.TypedArray          | typed array            |
+//  | js.Callback            | function               |
+//  | nil                    | null                   |
+//  | bool                   | boolean                |
+//  | integers and floats    | number                 |
+//  | string                 | string                 |
+//  | []interface{}          | new array              |
+//  | map[string]interface{} | new object             |
 func ValueOf(x interface{}) Value {
        switch x := x.(type) {
        case Value:
@@ -138,6 +143,18 @@ func ValueOf(x interface{}) Value {
                return floatValue(x)
        case string:
                return makeValue(stringVal(x))
+       case []interface{}:
+               a := arrayConstructor.New(len(x))
+               for i, s := range x {
+                       a.SetIndex(i, s)
+               }
+               return a
+       case map[string]interface{}:
+               o := objectConstructor.New()
+               for k, v := range x {
+                       o.Set(k, v)
+               }
+               return o
        default:
                panic("ValueOf: invalid value")
        }

diff --git a/src/syscall/js/js_test.go b/src/syscall/js/js_test.go
index 753e262d52e83f45c2073a124c1bf4a885c968c2..9cc931a31d38d99b3e465508fcc717410e555f70 100644 (file)
--- a/src/syscall/js/js_test.go
+++ b/src/syscall/js/js_test.go
@@ -254,6 +254,21 @@ func TestType(t *testing.T) {
        }
 }
 
+type object = map[string]interface{}
+type array = []interface{}
+
+func TestValueOf(t *testing.T) {
+       a := js.ValueOf(array{0, array{0, 42, 0}, 0})
+       if got := a.Index(1).Index(1).Int(); got != 42 {
+               t.Errorf("got %v, want %v", got, 42)
+       }
+
+       o := js.ValueOf(object{"x": object{"y": 42}})
+       if got := o.Get("x").Get("y").Int(); got != 42 {
+               t.Errorf("got %v, want %v", got, 42)
+       }
+}
+
 func TestCallback(t *testing.T) {
        c := make(chan struct{})
        cb := js.NewCallback(func(args []js.Value) {