WebAssembly.Table()

WebAssembly.Table()构造函数根据给定的大小和元素类型创建一个Table对象。

这是一个包装了WebAssemble Table 的Javascript包装对象，具有类数组结构，存储了多个函数引用。在Javascript或者WebAssemble中创建Table 对象可以同时被Javascript或WebAssemble 访问和更改。

Note: Tables 对象目前只能存储函数引用，不过在将来可能会被扩展。

Syntax

var myTable = new WebAssembly.Table(tableDescriptor);

Parameters

tableDescriptor该对象具有以下属性：element一个表明储存在该Table中对象的类型。目前只能是："anyfunc"(函数)。initial该WebAssembly Table初始大小。maximum 可选该WebAssembly Table允许扩展到的最大大小。

Exceptions

• 如果tableDescriptor不是对象类型,将会抛出TypeError异常。
• 如果申明了maximum属性并且比initial小,将会抛出RangeError异常。

Tableinstances

AllTableinstances inherit from theTable()constructor's prototype object — this can be modified to affect allTableinstances.

Instance properties

Table.prototype.constructorReturns the function that created this object's instance. By default this is theWebAssembly.Table()constructor.Table.prototype.lengthReturns the length of the table, i.e. the number of elements.

Instance methods

Table.prototype.get()Accessor function — gets the element stored at a given index.Table.prototype.grow()Increases the size of the Table instance by a specified number of elements.Table.prototype.set()Sets an element stored at a given index to a given value.

Examples

The following example(see table2.html source code and live version)creates a new WebAssembly Table instance with an initial size of 2 elements. We then print out the table length and contents of the two indexes(retrieved vianull.

var tbl = new WebAssembly.Table({initial:2, element:"anyfunc"});
console.log(tbl.length);  // "2"
console.log(tbl.get(0));  // "null"
console.log(tbl.get(1));  // "null"

We then create an import object that contains the table:

var importObj = {
  js: {
    tbl:tbl
  }
};

Finally, we load and instantiate a wasm module(table2.wasm)using theWebAssembly.instantiateStreaming()method. The table2.wasm module contains two functions(one that returns 42 and another that returns 83)and stores both into elements 0 and 1 of the imported table(see text representation). So after instantiation, the table still has length 2, but the elements now contain callable Exported WebAssembly Functions which we can call from JS.

WebAssembly.instantiateStreaming(fetch('table2.wasm'), importObject)
.then(function(obj) {
  console.log(tbl.length);
  console.log(tbl.get(0)());
  console.log(tbl.get(1)());
});

Note how you've got to include a second function invocation operator at the end of the accessor to actually invoke the referenced function and log the value stored inside it(e.g.get(0)()rather thanget(0)).

This example shows that we're creating and accessing the table from JavaScript, but the same table is visible and callable inside the wasm instance too.