Rx.Observable.prototype.pairwise()
Triggers on the second and subsequent triggerings of the input observable. The Nth triggering of the input observable passes the arguments from the N-1th and Nth triggering as a pair.
Returns
(Observable
): An observable that triggers on successive pairs of observations from the input observable as an array.
Example
var r = Rx.Observable.range(1, 4);
var source = r.pairwise();
var subscription = source.subscribe(
function (x) {
console.log('Next: ' + JSON.stringify(x));
},
function (err) {
console.log('Error: ' + err);
},
function () {
console.log('Completed');
});
// => Next: [1,2]
// => Next: [2,3]
// => Next: [3,4]
// => Completed
Example (Draw line)
<canvas id="canvas" width="600" height="600"/>
var canvas = document.getElementById("canvas");
var g = canvas.getContext("2d");
g.rect(0, 0, canvas.width, canvas.height);
g.fillStyle = "rgb(0,0,0)";
g.fill();
var mouseMove = Rx.Observable.fromEvent(document, 'mousemove');
var mouseDown = Rx.Observable.fromEvent(document.getElementById('canvas'), 'mousedown');
var mouseUp = Rx.Observable.fromEvent(document.getElementById('canvas'), 'mouseup');
mouseDown.flatMap(function(ev) {
return mouseMove.map(function(ev) {
return {
x: ev.clientX,
y: ev.clientY
};
}).pairwise().takeUntil(mouseUp);
}).subscribe(function(pos) {
g.beginPath();
g.lineWidth = 1;
g.strokeStyle = "rgb(255, 0, 0)";
g.moveTo(pos[0].x, pos[0].y);
g.lineTo(pos[1].x, pos[1].y);
g.stroke();
});
Location
File:
Dist:
NPM Packages:
NuGet Packages:
Unit Tests: