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// Package js provides functions for interacting with native JavaScript APIs. Calls to these functions are treated specially by GopherJS and translated directly to their corresponding JavaScript syntax.
//
// Use MakeWrapper to expose methods to JavaScript. When passing values directly, the following type conversions are performed:
//
// | Go type | JavaScript type | Conversions back to interface{} |
// | --------------------- | --------------------- | ------------------------------- |
// | bool | Boolean | bool |
// | integers and floats | Number | float64 |
// | string | String | string |
// | []int8 | Int8Array | []int8 |
// | []int16 | Int16Array | []int16 |
// | []int32, []int | Int32Array | []int |
// | []uint8 | Uint8Array | []uint8 |
// | []uint16 | Uint16Array | []uint16 |
// | []uint32, []uint | Uint32Array | []uint |
// | []float32 | Float32Array | []float32 |
// | []float64 | Float64Array | []float64 |
// | all other slices | Array | []interface{} |
// | arrays | see slice type | see slice type |
// | functions | Function | func(...interface{}) *js.Object |
// | time.Time | Date | time.Time |
// | - | instanceof Node | *js.Object |
// | maps, structs | instanceof Object | map[string]interface{} |
//
// Additionally, for a struct containing a *js.Object field, only the content of the field will be passed to JavaScript and vice versa.
package js
// Object is a container for a native JavaScript object. Calls to its methods are treated specially by GopherJS and translated directly to their JavaScript syntax. A nil pointer to Object is equal to JavaScript's "null". Object can not be used as a map key.
type Object struct{ object *Object }
// Get returns the object's property with the given key.
func (o *Object) Get(key string) *Object { return o.object.Get(key) }
// Set assigns the value to the object's property with the given key.
func (o *Object) Set(key string, value interface{}) { o.object.Set(key, value) }
// Delete removes the object's property with the given key.
func (o *Object) Delete(key string) { o.object.Delete(key) }
// Length returns the object's "length" property, converted to int.
func (o *Object) Length() int { return o.object.Length() }
// Index returns the i'th element of an array.
func (o *Object) Index(i int) *Object { return o.object.Index(i) }
// SetIndex sets the i'th element of an array.
func (o *Object) SetIndex(i int, value interface{}) { o.object.SetIndex(i, value) }
// Call calls the object's method with the given name.
func (o *Object) Call(name string, args ...interface{}) *Object { return o.object.Call(name, args...) }
// Invoke calls the object itself. This will fail if it is not a function.
func (o *Object) Invoke(args ...interface{}) *Object { return o.object.Invoke(args...) }
// New creates a new instance of this type object. This will fail if it not a function (constructor).
func (o *Object) New(args ...interface{}) *Object { return o.object.New(args...) }
// Bool returns the object converted to bool according to JavaScript type conversions.
func (o *Object) Bool() bool { return o.object.Bool() }
// String returns the object converted to string according to JavaScript type conversions.
func (o *Object) String() string { return o.object.String() }
// Int returns the object converted to int according to JavaScript type conversions (parseInt).
func (o *Object) Int() int { return o.object.Int() }
// Int64 returns the object converted to int64 according to JavaScript type conversions (parseInt).
func (o *Object) Int64() int64 { return o.object.Int64() }
// Uint64 returns the object converted to uint64 according to JavaScript type conversions (parseInt).
func (o *Object) Uint64() uint64 { return o.object.Uint64() }
// Float returns the object converted to float64 according to JavaScript type conversions (parseFloat).
func (o *Object) Float() float64 { return o.object.Float() }
// Interface returns the object converted to interface{}. See table in package comment for details.
func (o *Object) Interface() interface{} { return o.object.Interface() }
// Unsafe returns the object as an uintptr, which can be converted via unsafe.Pointer. Not intended for public use.
func (o *Object) Unsafe() uintptr { return o.object.Unsafe() }
// Error encapsulates JavaScript errors. Those are turned into a Go panic and may be recovered, giving an *Error that holds the JavaScript error object.
type Error struct {
*Object
}
// Error returns the message of the encapsulated JavaScript error object.
func (err *Error) Error() string {
return "JavaScript error: " + err.Get("message").String()
}
// Stack returns the stack property of the encapsulated JavaScript error object.
func (err *Error) Stack() string {
return err.Get("stack").String()
}
// Global gives JavaScript's global object ("window" for browsers and "GLOBAL" for Node.js).
var Global *Object
// Module gives the value of the "module" variable set by Node.js. Hint: Set a module export with 'js.Module.Get("exports").Set("exportName", ...)'.
var Module *Object
// Undefined gives the JavaScript value "undefined".
var Undefined *Object
// Debugger gets compiled to JavaScript's "debugger;" statement.
func Debugger() {}
// InternalObject returns the internal JavaScript object that represents i. Not intended for public use.
func InternalObject(i interface{}) *Object {
return nil
}
// MakeFunc wraps a function and gives access to the values of JavaScript's "this" and "arguments" keywords.
func MakeFunc(fn func(this *Object, arguments []*Object) interface{}) *Object {
return Global.Call("$makeFunc", InternalObject(fn))
}
// Keys returns the keys of the given JavaScript object.
func Keys(o *Object) []string {
if o == nil || o == Undefined {
return nil
}
a := Global.Get("Object").Call("keys", o)
s := make([]string, a.Length())
for i := 0; i < a.Length(); i++ {
s[i] = a.Index(i).String()
}
return s
}
// MakeWrapper creates a JavaScript object which has wrappers for the exported methods of i. Use explicit getter and setter methods to expose struct fields to JavaScript.
func MakeWrapper(i interface{}) *Object {
v := InternalObject(i)
o := Global.Get("Object").New()
o.Set("__internal_object__", v)
methods := v.Get("constructor").Get("methods")
for i := 0; i < methods.Length(); i++ {
m := methods.Index(i)
if m.Get("pkg").String() != "" { // not exported
continue
}
o.Set(m.Get("name").String(), func(args ...*Object) *Object {
return Global.Call("$externalizeFunction", v.Get(m.Get("prop").String()), m.Get("typ"), true).Call("apply", v, args)
})
}
return o
}
// NewArrayBuffer creates a JavaScript ArrayBuffer from a byte slice.
func NewArrayBuffer(b []byte) *Object {
slice := InternalObject(b)
offset := slice.Get("$offset").Int()
length := slice.Get("$length").Int()
return slice.Get("$array").Get("buffer").Call("slice", offset, offset+length)
}
// M is a simple map type. It is intended as a shorthand for JavaScript objects (before conversion).
type M map[string]interface{}
// S is a simple slice type. It is intended as a shorthand for JavaScript arrays (before conversion).
type S []interface{}
func init() {
// avoid dead code elimination
e := Error{}
_ = e
}
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