Strangely the for loop doesn't appear to be called. The alert will say 1 but 2 will not show. There aren't any errors in the console, and online code checkers (Specifically JShint.com) say nothing is wrong at all.

window.onLoad = function() {
    var l = 1;
    const S = "Spawn";
    const N = "Next";
    const K = "Kill";
    const LEVEL = [
        [
            [5, 5],
            [1, 1, 1, 1, 1],
            [1, 0, 0, 0, 1],
            [1, S, K, N, 1],
            [1, 0, 0, 0, 1],
            [1, 1, 1, 1, 1]
        ]
    ]
    const PSIZE = 54;
    var SCR = document.getElementById("SCR");
    const context = SCR.getContext("2d");
    drawMap();
}

function drawMap() {
    let w = LEVEL[l - 1][0][0];
    let h = LEVEL[l - 1][0][1];
    alert("1")
    for(let lx = 0; lx == w - 1; lx += 1) {
        for(let ly = 1; ly == h; ly += 1) {
            let tile = LEVEL[l - 1][ly][lx];
            switch(tile) {
                case 1:
                    context.fillColor = "grey";
                    break;
                case 0:
                    context.fillColor = "white";
                    break;
                default:
                    context.fillColor = "red";
                    break;
                    
            }
            alert(2)
            context.fillRect(((lx + 1) * PSIZE), ((ly + 1) * PSIZE), PSIZE, PSIZE);
        }
    }
}