HTML canvas textBaseline 属性

var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");

//Draw a red line at y = 100
ctx.strokeStyle = "red";
ctx.moveTo(5, 100);
ctx.lineTo(395, 100);
ctx.stroke();

ctx.font = "20px Arial"

//Place each word at y = 100 with different textBaseline values
ctx.textBaseline = "top";
ctx.fillText("Top", 5, 100);
ctx.textBaseline = "bottom";
ctx.fillText("Bottom", 50, 100);
ctx.textBaseline = "middle";
ctx.fillText("Middle", 120, 100);
ctx.textBaseline = "alphabetic";
ctx.fillText("Alphabetic", 190, 100);
ctx.textBaseline = "hanging";
ctx.fillText("Hanging", 290, 100);