anExpression lets you programmatically build JavaScript expressions, modify them, and then turn them into source code.
var anExpression = require("an-expression")
var javascriptToEzjs = require("javascript-to-ezjs")
var tree = anExpression.tree()
javascriptToEzjs("blah({\n a: 1,})", tree)Once we have built a tree, we can query the data. Here we'll iterate through the key value pairs on that object expression, and expect to see the number 1:
var objectExpressionId = tree.getListItem("arguments", tree.rootId(), 0)
tree.eachListItem(
"pairIds",
objectExpressionId,
function(pairId) {
var key = tree.getAttribute(tree, "key", pairId)
var parentId = tree.getAttribute("key", pairId)
var valueId = tree.getAttribute("valueId", pairId)
var number = tree.getAttribute("number", valueId)
if (number != 1) {
throw new Error("Bad number") }
if (parentId != tree.root().id) {
throw new Error("Bad root")}})We can also modify the tree:
tree.addKeyValuePair(
objectExpressionId,
"b",
tree.numberLiteral(2))And then dump the modified code:
// tree.toJavaScript() returns:
blah({
a: 1,
b: 2})Methods
// Adds an empty function literal at the next available position
tree.addExpressionAt(
tree.reservePosition(),
anExpression.functionLiteral())
// Add a string literal inside that function literal
var functionId = tree.rootId()
var stringLiteral = anExpression.stringLiteral("alert")
tree.addToParent(functionId, stringLiteral)Expression generators
var hello = anExpression.stringLiteral("hello, world")
// "hello, world"
anExpression.functionLiteral({
functionName: "add",
argumentNames: ["a", "b"],
body: hello})
// function add(a, b) {
// "hello, world"
// }
var a = anExpression.numberLiteral(42)
// 42
var b = anExpression.numberLiteral(1)
// 1
anExpression.functionCall({
functionName: "add",
arguments: [a, b]})
// add(42, 1)
anExpression.variableReference("a")
// a
anExpression.variableAssignment({
variableName: "a",
expression: "b"})
// a = b
anExpression.variableAssignment({
variableName: "c",
expression: "b",
isDeclaration: true})
// var c = b
anExpression.objectLiteral({
name: a.id
})
// {name: a}
anExpression.arrayLiteral([a.id, b.id])
// [a, b]
anExpression.boolean(true)
anExpression.true()
// true
anExpression.false()
// false
anExpression.returnStatement({
expression: a})
// return a
