Adjust imaginary tickvals default to fix react

[archmoj]

The magical default for imaginary tickvals added in #5956 (comment) broke the react ("noCi" plotl_api_react_test).

@plotly/plotly_js

[alexcjohnson]

I imagine the problem with this is we get a new array each time, so Plotly.react thinks this has changed and needs replotting? I do think as a default this behavior makes sense, can we fix it with a simple memoizer? Something like:

function memoize(fn, keyFn) {
    var cache = {};
    return function(val) {
        var newKey = keyFn ? keyFn(val) : val;
        if (newKey in cache) { return cache[newKey]; }
        out = fn(val);
        cache[newKey] = out;
        return out;
    }
}

var makeImagDflt = memoizeOne(function(realTickvals) {
    return realTickvals.slice().reverse().map(function(x) { return -x; })
        .concat([0])
        .concat(realTickvals);
}, String);

var a = makeImagDflt([2,4,5])
var b = makeImagDflt([2,4,5])
a===b // true

var c = makeImagDflt([1,2,3])
var d = makeImagDflt([2,4,5])
d===b // true

A memoizer might be useful in other contexts too... we use them quite a lot in Dash anyway.

[archmoj]

It's a kind of magic!
Applied in 844e24c

[alexcjohnson]

💃 🧙