[英]What should I do if text is not output from html5 canvas?
<script>
var canvas = document.getElementById('canvas'),
context = canvas.getContext('2d');
function numText(num,x,y)
{
this.num = num,
this.x = x,
this.y = y;
}
numText.prototype.writeText = function()
{
context.font ='60px Bahnschrift SemiCondensed';
context.fillStyle = 'red';
context.fillText(numText.text,numText.x,numText.y);
}
var text1 = new numText("30",100,225);
text1.writeText();
</script>
我想使用面向對象編程的概念打印出“30”。 文字不打印怎么辦?
你需要糾正兩件事:
writeText
numText
中用this
替換對 numText 的引用。this
關鍵字引用其屬性context.fillText
時,您使用的是屬性text
而不是num
作為第一個參數更正的代碼:
var canvas = document.getElementById('canvas'),
context = canvas.getContext('2d');
function numText(num, x, y) {
this.num = num,
this.x = x,
this.y = y;
}
numText.prototype.writeText = function () {
context.font = '60px Bahnschrift SemiCondensed';
context.fillStyle = 'red';
context.fillText(this.num, this.x, this.y);
}
var text1 = new numText("30", 100, 225);
text1.writeText();
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