Janko in a Jar

Jsgoo.js library is leaning towards functional ( FP ) style of programming. Besides the typical map, reduce and filter I added function I called seek. You can get the same result with reduce (this is sort of optimisation on a subset of reduce) but seek can exit iteration of sequence once it finds it’s return value, while reduce usually iterates whole to reduce it to a return value.

It’s definition goes like this:

seek: function (f, arr) {
    for (var i = 0; i < arr.length; i++) { var t = f(arr[i], i); if (t) return t; }
    return false;
}

A simple example of usage is function has. It checks if a value is in a sequence.

has: function (n, arr) {
    return this.seek(function(e, i){ return e == n; }, arr);
}

It can also be used in unpure manners to modify the data instead of just returning it. We use it in Data Resources part to do select, update, delete by Id:

deleteById: function (data, id) {
    return jsGooC.seek(function(x, i){ if (x.id==id){ data.splice(i, 1); return true } else { return false } }, data);
},

updateById: function (data, unit) {
    return jsGooC.seek(function(x, i){ if (x.id==unit.id){ data[i] = unit; return true } else { return false } }, data);
}

Perhaps the most interesting use of it in jsgoo itself is the equal function. It tests if two values (data structures) are equal. In JavaScript == doesn’t check for equality on objects and arrays:

equal: function (o1, o2) {
    return ! (
        o1 instanceof Array && o2 instanceof Array ||
        o1 instanceof Object && o2 instanceof Object ?
            jsgCore.seek( function ( o, i ) { return ! jsgCore.equal(o, o2[i] ) }, o1 )
        : o1 != o2
    );
}

Next time I will present how related seek functions can be used to elegantly traverse HTML DOM itself.

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