This is my search box

     <div id="search1"  style="margin:0;">
        <form action="<?php bloginfo('url'); ?>"  method="get">
          <input class="search-pishrafte1" name="s" value="Search" onfocus="if (this.value == 'Search') {this.value = '';}" onblur="if (this.value == '') {this.value = 'Search';}" type="text">
          <input class="searchsubmit" value="" type="submit">
        </form>
      </div>

right now if i click on submit it will search for text:"search" I want to disable it , i dont want the button to work when user didnt type anything

I tried this : Disable button whenever a text field is empty dynamically but didnt work

If using jQuery, I coded with hide() and show() functions
So will show button after input text or deleted button if empty input

I have code like that:

$(document).ready(function() {
  $('.searchsubmit').hide();
  $('input[type="text"].search-pishrafte1').keyup(function() {
    if ($(this).val() != '') {
      $('.searchsubmit').show();
    } else {
      $('.searchsubmit').hide();
    }
  });
});

And deleted your code in:

onfocus="if (this.value == 'Search') {this.value = '';}" onblur="if (this.value == '') {this.value = 'Search';}"

Here example

$(document).ready(function() {
  $('.searchsubmit').hide();
  $('input[type="text"].search-pishrafte1').keyup(function() {
    if ($(this).val() != '') {
      $('.searchsubmit').show();
    } else {
      $('.searchsubmit').hide();
    }
  });
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="search1" style="margin:0;">
  <form action="<?php bloginfo('url'); ?>" method="get">
    <input class="search-pishrafte1" name="s" placeholder="Search" type="text">
    <input class="searchsubmit" value="Submit" type="submit">
  </form>
</div>

UPDATED

let button = document.getElementById("search-btn")
let input = document.getElementById("input-search")

input.addEventListener("input", function(e) {
if(input.value.length == 0) {
  button.disabled = true
 } else {
  button.disabled = false
 }
})

In this code need addEventListener into input for detect input if typing

let button = document.getElementById("search-btn")
let input = document.getElementById("input-search")
input.addEventListener("input", function(e) {
    if(input.value.length == 0) {
    button.disabled = true
  } else {
    button.disabled = false
  }
})

<div id="search1"  style="margin:0;">
        <form action="<?php bloginfo('url'); ?>"  method="get">
          <input id="input-search" class="search-pishrafte1" name="s" placeholder="Search" type="text" required="required" />
          <input id="search-btn" class="searchsubmit" value="Submit" type="submit" disabled>
        </form>
      </div>

Then if you want if i click on submit it will search for text:"search" I want to disable it. You need a changed a value in input to placeholder.