在D3中的数据对象上调用具有多个参数的函数

Question

I'm new to D3 and JS and try to understand how to call a function with multiple parameters on a data object in D3. Below my attempt. The question is how would I make version 2 work?

d3.csv(input_file, function(data) {

    var metric = "foo";

    // Version 1:
    // clean number format. works fine
    data.forEach(function(d) {
        d[metric] = +d[metric].replace(/,/g,''); //remove thousand separator
        return d;
    });

    //Version 2:
    // this doesn't work. why not?
    // [Error] TypeError: undefined is not a function (evaluating 'd[metric].replace(/,/g,'')')
        data.forEach(function(d) {
          return cleanNumberFormat(d, metric);
        });

    // ...
});

// define a function to be used in several places
function cleanNumberFormat(d, metric) {
    d[metric] = +d[metric].replace(/,/g,''); //remove thousand separator
    return d;
}

Answer 1

The code works if you remove version 1 and leave version 2 alone. The root cause is this line in version 1:

d[metric] = +d[metric].replace(/,/g,''); //remove thousand separator

Note the plus sign + . It converts the replace result from type String to Number . Obviously Number does not have replace function, so you got the error in version 2.