Lua Requires Chilkat v11.4.0+

Call a JavaScript Function Returning an Integer

See more JavaScript Examples

Demonstrates how to call a JavaScript function that returns an integer. Lua

local chilkat = require("chilkat")

-- ----------------------------------------------------------------------------------
-- The Javascript function called in this example is shown at the bottom of this page.
-- -----------------------------------------------------------------------------------

-- In this example, we'll load the Javascript function definition from a file.
-- It doesn't need to come from a file.  It could just as easily be loaded from a string.
local sbScript = chilkat.StringBuilder.new()
local success = sbScript:load_file("js_call_function.js", "utf-8")
if not success then
    print(sbScript.last_error_text)
    return
end

-- Note: Each instance of a Chilkat Js object automatically establishes
-- its own internal runtime and context.  Applications do not need to explicitly create
-- the JavaScript runtime or context.
local js = chilkat.Js.new()

local result = chilkat.JsonObject.new()
result.emit_compact = false

-- Call Eval to add the function (shown at the bottom of this page) to the context's global object
success = js:eval(sbScript, result)
if not success then
    -- Examine the result for an exception.
    print(result:emit())

    -- Also examine the LastErrorText.
    print(js.last_error_text)
    return
end

print(result:emit())

-- The expected output is "undefined":

-- {
--   "type": "undefined",
--   "value": "undefined"
-- }

--    When Eval processes a script containing only a function declaration,
--    it successfully performs the action (the function becomes defined).
--    However, since the script consists of a statement that produces no value,
--    the script's overall completion value is empty. In JavaScript, the
--    absence of a value is represented by `undefined`.
--
--    Therefore, the Eval call returns `undefined`.

-- ------------------------------------------------------------------------------
-- Call the function calculateScore("Player1", 10, 20)

local funcCall = chilkat.JsonObject.new()

-- Create JSON defining the function call:

-- {
--   "name": "calculateScore",
--   "args": [ "Player1", 10, 20 ]
-- }

funcCall:update_string("name", "calculateScore")
funcCall:update_string("args[0]", "Player1")
funcCall:update_int("args[1]", 10)
funcCall:update_int("args[2]", 20)

funcCall.emit_compact = false
print(funcCall:emit())

success = js:call_function(funcCall, result)
if not success then
    -- Examine the result for an exception.
    print(result:emit())

    -- Also examine the LastErrorText.
    print(js.last_error_text)
    return
end

print(result:emit())

-- Output:

-- {
--   "type": "int",
--   "value": 37
-- }

local retval = result:int_of("value")
print("retval = " .. retval)

JavaScript

function calculateScore(name, pointsA, pointsB) {
    // Return length of name + both scores
    return name.length + pointsA + pointsB;
    }