Text Area maxlength not working

Question

I want to set maximum length to the textarea. I am using following code for the same,but it is not working,

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                <span>2021-01-18 02:34</span>
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<p><b> you can use</b></p>

<pre><code><textarea name="testString" onkeypress="if (this.value.length >= 250) { return false; }"id="" cols="30" rows="10" maxlength="250">