我花了两天时间寻找一种不添加插件的简单方法。

功能第一。定义api的php

//enqueue the script which will use the api
function api_callings_scripts() {
    wp_enqueue_script(\'score-script\', get_template_directory_uri() . \'/js/ScoreSaving.js\', [\'jquery\'], NULL, TRUE);
    // Pass nonce to JS.
    wp_localize_script(\'score-script\', \'ScoreSettings\', [
      \'nonce\' => wp_create_nonce(\'wp_rest\'),
    ]);
}
add_action( \'wp_enqueue_scripts\', \'api_callings_scripts\' ); 

jQuery.ajax({
      type: "POST",
      url: "/wp-json/score/update",
      data: {"var1":"value1"},
      beforeSend: function(xhr) {
        xhr.setRequestHeader(\'X-WP-Nonce\', ScoreSettings.nonce);
      },
    success: 
        function( data ) {
          console.log( data );
        }
    });