simple way to make a text field to accept numbers only with maximum number of length 13 digit and min 10

C++
<input name="phoneNumber"
    oninput="javascript: if (this.value.length > this.maxLength) this.value = this.value.slice(0, this.maxLength);"
    type = "number"
    maxlength = "10"
 />
Source

Also in C++: