HTML5 Canvas Grid-从输入中获取网格平方大小

Question

How can I get the value of the input and turn it into the size of the grid squares? When I use the input value, my grid is messed up, but when I hard code the grid square size it works fine.

Here is a codepen: https://codepen.io/ryan_pixelers/pen/NbqKMQ

and here is the code:

// get our canvas 
var grid = document.getElementById('grid');
hide(grid);

var horizontalSpace = 0;
var verticalSpace = 0;

var button = document.getElementById('gridControls');
button.onclick = drawCanvas;


function drawCanvas() {

show(grid);
var context = grid.getContext('2d');

// HERE: Why doesn't this work???
// var gridSize = document.getElementById('widthHeight').value;
var gridSize = 10;

// set the canvas style to positions absolute
// and set z-index high to keep it on top
grid.style.position = 'absolute';
grid.style.zIndex = '100000';

// get window width and height
var w = window.innerWidth;
var h = window.innerHeight;

// set the canvas width and height to be the window w/h
grid.width = w;
grid.height = h;

// create the horizontal lines
for(var horizontal = 0; horizontal < w; horizontal++) {
    context.beginPath();
    context.moveTo(0, horizontalSpace);
    context.lineTo(w, horizontalSpace);
    context.lineWidth = 1;
    context.strokeStyle = "lightblue";
    context.stroke();
    horizontalSpace += gridSize;
}

// create the vertical lines
for(var vertical = 0; vertical < h; vertical++) {
    context.beginPath();
    context.moveTo(verticalSpace, 0);
    context.lineTo(verticalSpace, h);
    context.lineWidth = 1;
    context.strokeStyle = "lightblue";
    context.stroke();
    verticalSpace += gridSize;
}

}

function hide(element) {
    element.style.display = 'none';
}

function show(element) {
    element.style.display = 'block';
} 

Try uncommenting the line where I try to set gridSize as the value of the input field and see the result. It messes up the grid spaces!

Any idea how to remedy this?

Thanks!

Answer 1

好了，想通了：我需要在值上使用parseInt（）。