javascript bind method parameters

Question

I saw examples of 2 types of bind calls. first kind is:

    const book = {
      title: 'Brave New World',
      author: 'Aldous Huxley',
    }

    function summary() {
      console.log(`${this.title} was written by ${this.author}.`)
    }

    const braveNewWorldSummary = summary.bind(book)

now "this" in summary is now bond to the "book" object

the second kind is:

  function utilizationUpdate(chart, data) {....}

  function utilizationInit(component, btnGroup, data){
        ....
        var myChart = new Chart(ctx, {....}
        $(btnGroup).on("change", function() {
                    ...
                    fetch('{% url 'api_utilization' fac.fac_id %}?measure=' + measure + '&{{ request.GET.urlencode() }}' )
                    .then(status)
                    .then(json)
                    .then(utilizationUpdate.bind(this, myChart));
                }
            });
        }

"chart" in utilizationUpdate() is now bond to myChart.

Why in first bind() example, "this" is not an argument to be passed? but it is specified in the second bind() example?

first param is this, subsequent are params, have a ponder at the docs. Your first example is not the same as second, in the second example, myChart is passed as first param chart in utilizationUpdate — Lawrence Cherone
– Lawrence Cherone, Commented May 13, 2021 at 21:08

Unmitigated · Accepted Answer · 2021-05-13 21:07:04Z

1

The first argument passed to bind is the this value and the other arguments are the additional arguments to the function. In the first case, it only sets the this value, while in the second case, it sets both the this value and the first argument. However, it is likely that the this value wasn't truly needed, so null could have been passed too.

answered May 13, 2021 at 21:07

Unmitigated

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