Callback Scope

Getting the scope right for your callback function may be tricky depending on what
your function does. Below are a few exmaples of how to wrap your function.

Pure function

In this example our function pureFunction does not call this and doesn’t interact with any external functions. We can pass the function without calling it
as the callback value, and pass an array of arguments to callbackArgs.


import test from "ava";

import { timeExecution } from "wedgetail";

function pureFunction(x, y){
  return x * y * x * y;
}

test("Can time a function", async t => {

    const allowedPerformance = {
        average: 0.001,
        high: 1,
        low: 0.001,
        percentiles: {
            ninetieth: 0.0004,
            ninetyFifth: 0.001,
            ninetyNinth: 0.001,
            tenth: 0.0005,
        },
    };

    const config = new ConfigClass({
      config: {
        key: 'value',
      }
    });

    const timings = await timeExecution({
        expectedTimings: allowedPerformance,
        numberOfExecutions: 5000,
        callback: pureFunction,
        callbackArgs: [
          1,
          2,
          3,
          4
        ]
    });

    t.true(timings.results.passed, "timings failed");
});

Function that needs this scope

In this example, the method ConfigClass#getConfig calls this.config. We can use a closure on the callback to ensure the scope of this stays with the config.


import test from "ava";

import { timeExecution } from "wedgetail";

class ConfigClass {
  constructor(options) {
    this.config = options.config;
  }

  getConfig(){
    return this.config;
  }
}

test("Can time a function", async t => {

    const allowedPerformance = {
        average: 0.001,
        high: 1,
        low: 0.001,
        percentiles: {
            ninetieth: 0.0004,
            ninetyFifth: 0.001,
            ninetyNinth: 0.001,
            tenth: 0.0005,
        },
    };

    const config = new ConfigClass({
      config: {
        key: 'value',
      }
    });

    const timings = await timeExecution({
        expectedTimings: allowedPerformance,
        numberOfExecutions: 5000,

        callback: () => {
            // Your function goes here
            config.getConfig();
        },
    });

    t.true(timings.results.passed, "timings failed");
});