Measuring text width/height without rendering

问题

Is there any way to get an estimate for text width without rendering the actual elements? Something like canvas TextMetrics?

Case: I need to estimate element heights for ReactList. To do that I'd need to know roughly how much space the text elements will need (or how many lines will they span).

eg.

render(){
    return <div><SomeComponentWithKnownDims/><p>{this.props.someText}</p></div>;
}

If I knew how wide someText would be rendered into one line and how long the line would be, I could easily come up with a decent estimate for the components height.

EDIT: Note that this is quite performance critical and DOM should not be touched

回答1:

Please check this. is a solution using canvas

function get_tex_width(txt, font) {
        this.element = document.createElement('canvas');
        this.context = this.element.getContext("2d");
        this.context.font = font;
        return this.context.measureText(txt).width;
    }
    alert('Calculated width ' + get_tex_width("Hello World", "30px Arial"));
    alert("Span text width "+$("span").width());

Demo using

EDIT

The solution using canvas is not the best, each browser deal different canvas size.

Here is a nice solution to get size of text using a temporary element. Demo

EDIT

The canvas spec doesn't give us a method for measuring the height of a string, so for this we can use parseInt(context.font). TO get width and height. This trick work only with px size.

function get_tex_size(txt, font) {
    this.element = document.createElement('canvas');
    this.context = this.element.getContext("2d");
    this.context.font = font;
    var tsize = {'width':this.context.measureText(txt).width, 'height':parseInt(this.context.font)};
    return tsize;
}
var tsize = get_tex_size("Hello World", "30px Arial");

alert('Calculated width ' + tsize['width'] + '; Calculated height ' + tsize['height']);

来源：https://stackoverflow.com/questions/31305071/measuring-text-width-height-without-rendering