second commit

.gitignore

@@ -0,0 +1 @@
+/out/

.travis.yml

@@ -0,0 +1,12 @@
+language: go
+go:
+  - "1.10"
+install:
+  - make install
+script:
+  - "echo '{\"key\":\"value\"}' | go run main.go"
+  - "echo '{\"foo\": [{\"bar\": \"value\"}]}' | go run main.go 'this.foo[0].bar'"
+  - "echo '{\"foo\": [{\"bar\": \"value\"}]}' | go run main.go 'this.foo' 'this[0]' 'this.bar'"
+  - "echo '[]' | go run main.go 'void 0'"
+  - "echo '{\"foo\": 1, \"bar\": 2}' | go run main.go 'Object.keys(this)'"
+  - "echo '{\"foo\": 1, \"bar\": 2}' | go run main.go ?"

Makefile

@@ -0,0 +1,8 @@
+.PHONY: install build
+
+install:
+	go get github.com/robertkrimen/otto
+	go get github.com/hokaccha/go-prettyjson
+
+build:
+	gox -output "out/{{.Dir}}_{{.OS}}_{{.Arch}}"

README.md

@@ -1,4 +1,6 @@
-# XX
+<img src="https://user-images.githubusercontent.com/141232/41759457-dbfb230a-7618-11e8-9159-03aa62e57152.png" height="100" alt="fx">
+
+# [![Build Status](https://travis-ci.org/antonmedv/xx.svg?branch=master)](https://travis-ci.org/antonmedv/xx)
 
 [fx](https://github.com/antonmedv/fx)-like command-line JSON processing tool 
 
@@ -7,7 +9,12 @@
 * Don't need to learn new syntax
 * Plain JavaScript
 * Formatting and highlighting
-* Small binary size
+
+## Differences
+
+* Only ES5 (no arrow functions, no spread)
+* Small binary size (xx ~5mb vs fx ~30mb)
+* Can't use npm packages
 
 ## Install
 
@@ -54,15 +61,27 @@ $ echo '{"foo": [{"bar": "value"}]}' | xx 'this.foo' 'this[0]' 'this.bar'
 If you need something different then JSON (for example arguments for xargs) do not return anything from reducer.
 `undefined` value printed into stderr by default.
 ```
-echo '[]' | xx 'void 0'
+$ echo '[]' | xx 'void 0'
 undefined
 ```
 
 ```
-echo '[1,2,3]' | xx 'this.forEach(function (x) {console.log(x)})' 2>/dev/null | xargs echo
+$ echo '[1,2,3]' | xx 'this.forEach(function (x) { console.log(x) })' 2>/dev/null | xargs echo
 1 2 3
 ```
 
+### Modifying
+
+To modify object use command separated by comma `,` and return `this` as the end.
+
+```
+$ echo '{"a": 2}' | xx 'this["b"] = Math.pow(this.a, 10), this'
+{
+  "a": 2,
+  "b": 1024
+}
+``` 
+
 ### Object keys
 
 Get all object keys:
@@ -87,4 +106,4 @@ $ echo '{"foo": 1, "bar": 2}' | xx ?
 
 ## License
 
-MIT
+MIT

main.go

@@ -14,33 +14,33 @@ var vm = otto.New()
 func main() {
 	fi, err := os.Stdin.Stat()
 	if err != nil {
-		panic(err)
+		fatal(err)
 	}
-	if fi.Size() == 0 {
+	if fi.Mode()&os.ModeNamedPipe == 0 {
 		usage()
 		os.Exit(1)
 	}
 
 	buf, err := ioutil.ReadAll(os.Stdin)
 	if err != nil {
-		panic(err)
+		fatal(err)
 	}
 	var input interface{}
 	if err := json.Unmarshal(buf, &input); err != nil {
-		panic(err)
+		fatal(err)
 	}
 
 	if err := vm.Set("json", input); err != nil {
-		panic(err)
+		fatal(err)
 	}
 	value, err := vm.Get("json")
 	if err != nil {
-		panic(err)
+		fatal(err)
 	}
 	for _, code := range os.Args[1:] {
 		value, err = reduce(value, code)
 		if err != nil {
-			panic(err)
+			fatal(err)
 		}
 	}
 
@@ -51,18 +51,18 @@ func main() {
 
 	i, err := value.Export()
 	if err != nil {
-		panic(err)
+		fatal(err)
 	}
 	s, err := prettyjson.Marshal(i)
 	if err != nil {
-		panic(err)
+		fatal(err)
 	}
 	fmt.Println(string(s))
 }
 
 func reduce(value otto.Value, code string) (otto.Value, error) {
 	if err := vm.Set("json", value); err != nil {
-		panic(err)
+		fatal(err)
 	}
 	switch code {
 	case "?":
@@ -94,3 +94,8 @@ func usage() {
 
 `)
 }
+
+func fatal(err error) {
+	fmt.Fprintln(os.Stderr, err)
+	os.Exit(1)
+}